protect Widget._style_sheet_changed from being called before _control exists

also ensure _control attributes start out as None, rather than undefined

IPython/frontend/qt/console/console_widget.py

@@ -138,6 +138,11 b' class ConsoleWidget(LoggingConfigurable, QtGui.QWidget):'
 
     #------ Protected class variables ------------------------------------------
 
+    # control handles
+    _control = None
+    _page_control = None
+    _splitter = None
+    
     # When the control key is down, these keys are mapped.
     _ctrl_down_remap = { QtCore.Qt.Key_B : QtCore.Qt.Key_Left,
                          QtCore.Qt.Key_F : QtCore.Qt.Key_Right,
@@ -182,8 +187,6 b' class ConsoleWidget(LoggingConfigurable, QtGui.QWidget):'
         layout = QtGui.QStackedLayout(self)
         layout.setContentsMargins(0, 0, 0, 0)
         self._control = self._create_control()
-        self._page_control = None
-        self._splitter = None
         if self.paging in ('hsplit', 'vsplit'):
             self._splitter = QtGui.QSplitter()
             if self.paging == 'hsplit':

IPython/frontend/qt/console/ipython_widget.py

@@ -533,13 +533,15 b' class IPythonWidget(FrontendWidget):'
         """ Set the style sheets of the underlying widgets.
         """
         self.setStyleSheet(self.style_sheet)
+        if self._control is not None:
         self._control.document().setDefaultStyleSheet(self.style_sheet)
-        if self._page_control:
-            self._page_control.document().setDefaultStyleSheet(self.style_sheet)
-
         bg_color = self._control.palette().window().color()
         self._ansi_processor.set_background_color(bg_color)
 
+        if self._page_control is not None:
+            self._page_control.document().setDefaultStyleSheet(self.style_sheet)
+
+
 
     def _syntax_style_changed(self):
         """ Set the style for the syntax highlighter.