Only add newline when insert row exceeds last row

Previously if the line before a trailing newline was
duplicated an extra newline would inserted with the
duplicated line.

spec/app/editor-spec.coffee

@@ -2680,6 +2680,18 @@ describe "Editor", ->
           expect(buffer.lineForRow(15)).toBeUndefined()
           expect(editor.getCursorBufferPosition()).toEqual [14, 0]
 
+      describe "when the cursor is on the second to last line and the last line only a newline", ->
+        it "duplicates the current line below and moves the cursor down one row", ->
+          editor.moveCursorToBottom()
+          editor.insertNewline()
+          editor.setCursorBufferPosition([12])
+          editor.trigger 'editor:duplicate-line'
+          expect(buffer.lineForRow(12)).toBe '};'
+          expect(buffer.lineForRow(13)).toBe '};'
+          expect(buffer.lineForRow(14)).toBe ''
+          expect(buffer.lineForRow(15)).toBeUndefined()
+          expect(editor.getCursorBufferPosition()).toEqual [13, 0]
+
   describe ".moveEditSessionToIndex(fromIndex, toIndex)", ->
     describe "when the edit session moves to a later index", ->
       it "updates the edit session order", ->

src/app/edit-session.coffee

@@ -421,7 +421,7 @@ class EditSession
         bufferRange = new Range([cursorPosition.row], [cursorPosition.row + 1])
 
       insertPosition = new Point(bufferRange.end.row)
-      if insertPosition.row >= @buffer.getLastRow()
+      if insertPosition.row > @buffer.getLastRow()
         @unfoldCurrentRow() if cursorRowFolded
         @buffer.append("\n#{@getTextInBufferRange(bufferRange)}")
         @foldCurrentRow() if cursorRowFolded