Backport PR #2101: fix completer deletting newline

should fixes  #2082

do not forget to backport to 0.13.1

IPython/frontend/qt/console/console_widget.py

@@ -884,9 +884,10 b' class ConsoleWidget(LoggingConfigurable, QtGui.QWidget):'
             the prompt region.
         """
         # Select and remove all text below the input buffer.
-        _temp_buffer_filled = False
         cursor = self._get_prompt_cursor()
         prompt = self._continuation_prompt.lstrip()
+        if(self._temp_buffer_filled):
+            self._temp_buffer_filled = False
         while cursor.movePosition(QtGui.QTextCursor.NextBlock):
             temp_cursor = QtGui.QTextCursor(cursor)
             temp_cursor.select(QtGui.QTextCursor.BlockUnderCursor)
@@ -945,7 +946,7 b' class ConsoleWidget(LoggingConfigurable, QtGui.QWidget):'
         self._control.moveCursor(QtGui.QTextCursor.End)
         self._control.setTextCursor(cursor)
 
-        _temp_buffer_filled = True
+        self._temp_buffer_filled = True
 
 
     def _context_menu_make(self, pos):