Merge pull request biolab#1827 from janezd/fix-crash-cmd-c

[FIX] Crash on ctrl-c/cmd-c in widgets without graphs
(cherry picked from commit be22b64)

Author: lanzagar

Orange/widgets/widget.py

@@ -339,10 +339,11 @@ def save_graph(self):
         saveplot.save_plot(graph_obj, self.graph_writers)
 
     def copy_to_clipboard(self):
-        graph_obj = getdeepattr(self, self.graph_name, None)
-        if graph_obj is None:
-            return
-        ClipboardFormat.write_image(None, graph_obj)
+        if self.graph_name:
+            graph_obj = getdeepattr(self, self.graph_name, None)
+            if graph_obj is None:
+                return
+            ClipboardFormat.write_image(None, graph_obj)
 
     def __restoreWidgetGeometry(self):