Fixing up inline refactoring

[aclement]

Seen this whilst refactoring, didn't quite get the keystrokes that led to it:

Uncaught TypeError: Cannot call method 'substring' of undefined textModel.js:377
TextModel.getText textModel.js:377
UndoStack._onChanging undoStack.js:377
UndoStack._listener.onChanging undoStack.js:144
EventTarget._dispatchEvent eventTarget.js:76
EventTarget.dispatchEvent eventTarget.js:62
TextModel.onChanging textModel.js:398
TextModel.setText textModel.js:514
ProjectionTextModel.setText projectionTextModel.js:546
TextView._modifyContent textView.js:5154
InlineRenameRefactoringMode.handleKeyPress InlineRenameRefactoring.js:168
TextView._handleKeyPress textView.js:2832
handlers.push.handler