Throw on non-release builds if translating positions on destroyed editor

It’s possible that bundled packages stray into this corner case, so I’d
like us to catch and fix misbehaving packages before exposing users to 
any exceptions. Once we go one release with this turned on, we can
enable the exception for all builds.

src/display-buffer.coffee

@@ -736,6 +736,10 @@ class DisplayBuffer extends Model
   #
   # Returns a {Point}.
   screenPositionForBufferPosition: (bufferPosition, options) ->
+    # TODO: Expand this exception to cover all versions once we burn it in on non-release builds
+    if @isDestroyed() and not atom.isReleasedVersion()
+      throw new Error("This TextEditor has been destroyed")
+
     { row, column } = @buffer.clipPosition(bufferPosition)
     [startScreenRow, endScreenRow] = @rowMap.screenRowRangeForBufferRow(row)
     for screenRow in [startScreenRow...endScreenRow]
@@ -1073,7 +1077,7 @@ class DisplayBuffer extends Model
       marker.notifyObservers(textChanged: false)
 
   destroyed: ->
-    marker.unsubscribe() for marker in @getMarkers()
+    marker.unsubscribe() for id, marker of @markers
     @tokenizedBuffer.destroy()
     @unsubscribe()
 

src/text-editor-component.coffee

@@ -55,6 +55,8 @@ TextEditorComponent = React.createClass
     hasSelection = editor.getLastSelection()? and !editor.getLastSelection().isEmpty()
     style = {}
 
+    @performedInitialMeasurement = false if editor.isDestroyed()
+
     if @performedInitialMeasurement
       renderedRowRange = @getRenderedRowRange()
       [renderedStartRow, renderedEndRow] = renderedRowRange
@@ -227,10 +229,10 @@ TextEditorComponent = React.createClass
     @props.editor.setVisible(true)
     @performedInitialMeasurement = true
     @updatesPaused = false
-    @forceUpdate() if @updateRequestedWhilePaused
+    @forceUpdate() if @updateRequestedWhilePaused and @canUpdate()
 
   requestUpdate: ->
-    return unless @isMounted()
+    return unless @canUpdate()
 
     if @updatesPaused
       @updateRequestedWhilePaused = true
@@ -242,7 +244,10 @@ TextEditorComponent = React.createClass
       @updateRequested = true
       requestAnimationFrame =>
         @updateRequested = false
-        @forceUpdate() if @isMounted()
+        @forceUpdate() if @canUpdate()
+
+  canUpdate: ->
+    @isMounted() and @props.editor.isAlive()
 
   requestAnimationFrame: (fn) ->
     @updatesPaused = true
@@ -250,7 +255,7 @@ TextEditorComponent = React.createClass
     requestAnimationFrame =>
       fn()
       @updatesPaused = false
-      if @updateRequestedWhilePaused and @isMounted()
+      if @updateRequestedWhilePaused and @canUpdate()
         @updateRequestedWhilePaused = false
         @forceUpdate()
 
@@ -773,7 +778,7 @@ TextEditorComponent = React.createClass
     if position is 'absolute' or height
       if @autoHeight
         @autoHeight = false
-        @forceUpdate() unless @updatesPaused
+        @forceUpdate() if not @updatesPaused and @canUpdate()
 
       clientHeight =  scrollViewNode.clientHeight
       editor.setHeight(clientHeight) if clientHeight > 0

src/text-editor-element.coffee

@@ -37,6 +37,8 @@ class TextEditorElement extends HTMLElement
 
   setModel: (model) ->
     throw new Error("Model already assigned on TextEditorElement") if @model?
+    return if model.isDestroyed()
+
     @model = model
     @mountComponent()
     @addGrammarScopeAttribute()