added try block to backend_gtk3.py

Added try block around `draw` in `idle_draw`. If `draw` raises an exception the figure is never marked idle again and pyplot functions will not work as expect.
matplotlib · pelson · Dec 18, 2013 · Dec 12, 2013 · Dec 14, 2013 · Dec 14, 2013
commit ed8e3576491030ab927abbfb0380c22f69e27dd5
diff --git a/lib/matplotlib/backends/backend_gtk3.py b/lib/matplotlib/backends/backend_gtk3.py
@@ -322,8 +322,10 @@ def draw(self):

    def draw_idle(self):
        def idle_draw(*args):
-            self.draw()
-            self._idle_draw_id = 0
+            try:
+                self.draw()
+            finally:
+                self._idle_draw_id = 0
            return False
        if self._idle_draw_id == 0:
            self._idle_draw_id = GObject.idle_add(idle_draw)