Calculate gutter dimensions when editor's dimensions are calculated

src/app/editor.coffee

@@ -499,7 +499,7 @@ class Editor extends View
     rootView.on "font-size-change.editor#{@id}", => @setFontSize(rootView.getFontSize())
 
   setFontSize: (fontSize) ->
-    if fontSize
+    if fontSize?
       @css('font-size', fontSize + 'px')
       @calculateDimensions()
       @updateCursorViews()
@@ -627,6 +627,8 @@ class Editor extends View
     @height(@lineHeight) if @mini
     fragment.remove()
 
+    @gutter.calculateDimensions()
+
   prepareForScrolling: ->
     @adjustHeightOfRenderedLines()
     @adjustWidthOfRenderedLines()

src/app/gutter.coffee

@@ -9,14 +9,19 @@ class Gutter extends View
     @div class: 'gutter', =>
       @div outlet: 'lineNumbers', class: 'wtf'
 
-  renderLineNumbers: (startScreenRow, endScreenRow) ->
+  editor: ->
     editor = @parentView
+
+  renderLineNumbers: (startScreenRow, endScreenRow) ->
     lastScreenRow = -1
-    rows = editor.bufferRowsForScreenRows(startScreenRow, endScreenRow)
+    rows = @editor().bufferRowsForScreenRows(startScreenRow, endScreenRow)
 
     @lineNumbers[0].innerHTML = $$$ ->
       for row in rows
         @div {class: 'line-number'}, if row == lastScreenRow then '•' else row + 1
         lastScreenRow = row
 
-    @lineNumbers.width(editor.buffer.getLastRow().toString().length * editor.charWidth)
+    @calculateDimensions()
+
+  calculateDimensions: ->
+    @lineNumbers.width(@editor().buffer.getLastRow().toString().length * @editor().charWidth)