No longer push empty batches onto undo stack

spec/app/undo-manager-spec.coffee

@@ -136,3 +136,12 @@ describe "UndoManager", ->
 
       expect(buffer.lineForRow(4)).not.toContain("while")
       expect(buffer.lineForRow(4)).toContain("slongaz")
+
+   it "does not store empty batches", ->
+      buffer.insert([0,0], "foo")
+      undoManager.startUndoBatch()
+      undoManager.endUndoBatch()
+
+      undoManager.undo()
+      expect(buffer.lineForRow(0)).not.toContain("foo")
+

src/app/undo-manager.coffee

@@ -40,7 +40,7 @@ class UndoManager
 
   endUndoBatch: (ranges) ->
     @currentBatch.newSelectionRanges = ranges
-    @undoHistory.push(@currentBatch)
+    @undoHistory.push(@currentBatch) if @currentBatch.length > 0
     @currentBatch = null
 
   preservingHistory: (fn) ->