ESC should be handled by CM if tooltip is not on

IPython/html/static/notebook/js/codecell.js

@@ -179,8 +179,12 b' var IPython = (function (IPython) {'
                 return true;
             };
         } else if (event.which === key.ESC) {
+            if (!IPython.tooltip._hidden) {
             IPython.tooltip.remove_and_cancel_tooltip(true);
             return true;
+            } else {
+              return false;
+            }
         } else if (event.which === key.DOWNARROW && event.type === 'keydown') {
             // If we are not at the bottom, let CM handle the down arrow and
             // prevent the global keydown handler from handling it.