Don't throw exceptions when using editor APIs after destroying the editor

Signed-off-by: Nathan Sobo <nathan@github.com>

src/cursor.coffee

@@ -26,7 +26,6 @@ class Cursor extends Model
 
   destroy: ->
     @marker.destroy()
-    @marker = null
 
   ###
   Section: Event Subscription

src/selection.coffee

@@ -26,8 +26,6 @@ class Selection extends Model
 
   destroy: ->
     @marker.destroy()
-    @marker = null
-    @decoration = null
 
   isLastSelection: ->
     this is @editor.getLastSelection()

src/text-editor.coffee

@@ -409,24 +409,14 @@ class TextEditor extends Model
 
   destroyed: ->
     @emitter.emit 'did-destroy'
-    @emitter = null
+    @emitter.clear()
     @disposables.dispose()
     @displayLayer.destroy()
-    @displayLayer = null
-    @defaultMarkerLayer = null
     @tokenizedBuffer.destroy()
-    @tokenizedBuffer = null
     selection.destroy() for selection in @selections.slice()
-    @selections = null
-    @cursors = null
-    @selectionsMarkerLayer = null
     @buffer.release()
-    @buffer = null
-    @decorationManager = null
     @languageMode.destroy()
-    @languageMode = null
     @gutterContainer.destroy()
-    @gutterContainer = null
     @editorElement = null
     @presenter = null
 

src/tokenized-buffer.coffee

@@ -41,6 +41,7 @@ class TokenizedBuffer extends Model
 
   destroyed: ->
     @disposables.dispose()
+    @tokenizedLines.length = 0
 
   buildIterator: ->
     new TokenizedBufferIterator(this)
@@ -94,6 +95,7 @@ class TokenizedBuffer extends Model
     false
 
   retokenizeLines: ->
+    return unless @alive
     @fullyTokenized = false
     @tokenizedLines = new Array(@buffer.getLineCount())
     @invalidRows = []