💂‍♂️ Add guard when creating binding without a minimap

Should prevent errors reported in #17

Author: abe33

lib/minimap-git-diff-binding.coffee

@@ -7,11 +7,15 @@ class MinimapGitDiffBinding
   active: false
 
   constructor: (@minimap) ->
-    @editor = @minimap.getTextEditor()
     @decorations = {}
     @markers = null
     @subscriptions = new CompositeDisposable
 
+    unless @minimap?
+      return console.warn 'minimap-git-diff binding created without a minimap'
+
+    @editor = @minimap.getTextEditor()
+
     @subscriptions.add @editor.getBuffer().onDidStopChanging @updateDiffs
     @subscriptions.add @minimap.onDidDestroy @destroy