Move ahead/behind defaults to Git class

src/app/git.coffee

@@ -141,7 +141,7 @@ class Git
     directoryStatus
 
   getAheadBehindCounts: ->
-    @getRepo().getAheadBehindCounts()
+    @getRepo().getAheadBehindCounts() ? ahead: 0, behind: 0
 
   getLineDiffs: (path, text) ->
     @getRepo().getLineDiffs(@relativize(path), text) ? []

src/app/repository-status-handler.coffee

@@ -9,7 +9,7 @@ module.exports =
       statuses = {}
       for path, status of repo.getRepo().getStatuses()
         statuses[fs.join(workingDirectoryPath, path)] = status
-      upstream = repo.getAheadBehindCounts() ? {ahead: 0, behind: 0}
+      upstream = repo.getAheadBehindCounts()
       repo.destroy()
     else
       upstream = {}