added try block in backend_tkagg.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 a6fbc7fa90b09d0abac83b97ae36553727620f61
diff --git a/lib/matplotlib/backends/backend_tkagg.py b/lib/matplotlib/backends/backend_tkagg.py
@@ -362,8 +362,10 @@ def draw_idle(self):
        d = self._idle
        self._idle = False
        def idle_draw(*args):
-            self.draw()
-            self._idle = True
+            try:
+                self.draw()
+            finally:
+                self._idle = True

        if d:
            self._idle_callback = self._tkcanvas.after_idle(idle_draw)