StringIndexOutOfBoundsException in certain scenario when deleting lines in a rich text

[malueck]

Related to issue 647.

Steps to reproduce: Set the content of a Text to a number of newlines.
Empty lines are marked with "." here.
Set the cursor (here: "|") on the last line.
Example:

.
.
.
.
|

Press Shift-Upwards to select (shown by []) the empty lines except the first.
MPS will show "boxes" like this for the selection, it will not show a box for the last line (which should be also marked).

.
[]
[]
[]
.

Press Backspace/Delete once, it will delete the empty lines except one which is still selected:

.
[]

Press Backspace/Delete again, or change the selection with e.g. Rightarrow, an exception will occur:

Action dispatch failed. Thread AWT-EventQueue-0, state ACTIVE, 1 active clients.

java.lang.StringIndexOutOfBoundsException: begin 4, end 1, length 1
	at java.base/java.lang.String.checkBoundsBeginEnd(String.java:4602)
	at java.base/java.lang.String.substring(String.java:2705)
	at de.slisson.mps.richtext.runtime.selection.RichtextSelection.deleteSelected(RichtextSelection.java:510)
	at de.slisson.mps.richtext.runtime.selection.RichtextSelection.lambda$executeDeleteSelected$4(RichtextSelection.java:449)
	at jetbrains.mps.smodel.WorkbenchModelAccess$UndoContextSetup.run(WorkbenchModelAccess.java:367)
	at jetbrains.mps.smodel.ActionDispatcher.dispatch(ActionDispatcher.java:98)
	at jetbrains.mps.smodel.ActionDispatcher.lambda$wrap$0(ActionDispatcher.java:135)
	at jetbrains.mps.smodel.ActionDispatcher.dispatch(ActionDispatcher.java:98)
	at jetbrains.mps.smodel.ActionDispatcher.lambda$wrap$0(ActionDispatcher.java:135)
	at jetbrains.mps.smodel.LockRunnable.run(LockRunnable.java:60)
	at jetbrains.mps.smodel.TryRunPlatformWriteHelper.lambda$tryWrite$2(TryRunPlatformWriteHelper.java:122)
	at com.intellij.openapi.application.impl.ApplicationImpl.runWriteAction(ApplicationImpl.java:1023)
	at jetbrains.mps.smodel.TryRunPlatformWriteHelper.runWrite(TryRunPlatformWriteHelper.java:103)
	at jetbrains.mps.smodel.TryRunPlatformWriteHelper.tryWrite(TryRunPlatformWriteHelper.java:120)
	at jetbrains.mps.smodel.WorkbenchModelAccess.lambda$tryWriteInCommand$3(WorkbenchModelAccess.java:218)
	at jetbrains.mps.util.ComputeRunnable.compute(ComputeRunnable.java:32)
	at jetbrains.mps.util.AbstractComputeRunnable.run(AbstractComputeRunnable.java:27)
	at com.intellij.openapi.command.impl.CoreCommandProcessor.executeCommand(CoreCommandProcessor.java:219)
	at com.intellij.openapi.command.impl.CoreCommandProcessor.executeCommand(CoreCommandProcessor.java:174)
	at com.intellij.openapi.command.impl.CoreCommandProcessor.executeCommand(CoreCommandProcessor.java:164)
	at jetbrains.mps.smodel.WorkbenchModelAccess.tryWriteInCommand(WorkbenchModelAccess.java:235)
	at jetbrains.mps.smodel.WorkbenchModelAccess.lambda$runCommandInEDT_$2(WorkbenchModelAccess.java:151)
	at jetbrains.mps.smodel.EDTExecutor$1.tryRun(EDTExecutor.java:61)
	at jetbrains.mps.smodel.EDTExecutorInternal.tryToRunTopTask(EDTExecutorInternal.java:296)
	at jetbrains.mps.smodel.EDTExecutorInternal.flushNTasks(EDTExecutorInternal.java:251)
	at jetbrains.mps.smodel.EDTExecutorInternal.doFlush(EDTExecutorInternal.java:233)
	at jetbrains.mps.smodel.EDTExecutorInternal.flushTasksQueue(EDTExecutorInternal.java:213)
	at jetbrains.mps.smodel.EDTExecutorInternal.lambda$guaranteeWriteSafetyViaHack$2(EDTExecutorInternal.java:200)
	at com.intellij.openapi.application.TransactionGuardImpl.runWithWritingAllowed(TransactionGuardImpl.java:209)
	at com.intellij.openapi.application.TransactionGuardImpl.access$100(TransactionGuardImpl.java:21)
	at com.intellij.openapi.application.TransactionGuardImpl$1.run(TransactionGuardImpl.java:191)
	at jetbrains.mps.smodel.EDTExecutorInternal.lambda$guaranteeWriteSafetyViaHack$3(EDTExecutorInternal.java:205)
	at jetbrains.mps.smodel.EDTExecutorInternal.lambda$forceScheduleFlushEDT$1(EDTExecutorInternal.java:168)
	at com.intellij.openapi.application.TransactionGuardImpl$1.run(TransactionGuardImpl.java:194)
	at com.intellij.openapi.application.impl.ApplicationImpl.runIntendedWriteActionOnCurrentThread(ApplicationImpl.java:881)
	at com.intellij.openapi.application.impl.ApplicationImpl$3.run(ApplicationImpl.java:513)
	at com.intellij.openapi.application.impl.FlushQueue.doRun(FlushQueue.java:75)
	at com.intellij.openapi.application.impl.FlushQueue.runNextEvent(FlushQueue.java:118)
	at com.intellij.openapi.application.impl.FlushQueue.flushNow(FlushQueue.java:42)
	at java.desktop/java.awt.event.InvocationEvent.dispatch(InvocationEvent.java:318)
	at java.desktop/java.awt.EventQueue.dispatchEventImpl(EventQueue.java:779)
	at java.desktop/java.awt.EventQueue$4.run(EventQueue.java:730)
	at java.desktop/java.awt.EventQueue$4.run(EventQueue.java:724)
	at java.base/java.security.AccessController.doPrivileged(AccessController.java:399)
	at java.base/java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:86)
	at java.desktop/java.awt.EventQueue.dispatchEvent(EventQueue.java:749)
	at com.intellij.ide.IdeEventQueue.defaultDispatchEvent(IdeEventQueue.java:918)
	at com.intellij.ide.IdeEventQueue._dispatchEvent(IdeEventQueue.java:766)
	at com.intellij.ide.IdeEventQueue.lambda$dispatchEvent$6(IdeEventQueue.java:450)
	at com.intellij.openapi.progress.impl.CoreProgressManager.computePrioritized(CoreProgressManager.java:791)
	at com.intellij.ide.IdeEventQueue.lambda$dispatchEvent$7(IdeEventQueue.java:449)
	at com.intellij.openapi.application.TransactionGuardImpl.performActivity(TransactionGuardImpl.java:105)
	at com.intellij.ide.IdeEventQueue.performActivity(IdeEventQueue.java:624)
	at com.intellij.ide.IdeEventQueue.lambda$dispatchEvent$8(IdeEventQueue.java:447)
	at com.intellij.openapi.application.impl.ApplicationImpl.runIntendedWriteActionOnCurrentThread(ApplicationImpl.java:881)
	at com.intellij.ide.IdeEventQueue.dispatchEvent(IdeEventQueue.java:493)
	at java.desktop/java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:207)
	at java.desktop/java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:128)
	at java.desktop/java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:117)
	at java.desktop/java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:113)
	at java.desktop/java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:105)
	at java.desktop/java.awt.EventDispatchThread.run(EventDispatchThread.java:92)

The above stacktrace is in MPS Extensions 2022.2, but probably looks similar with newer versions.