Fix operator execution resetting the cursor

Area and region are NULL in the context if the operator finishes.

source/blender/windowmanager/intern/wm_event_system.c

@@ -1958,7 +1958,7 @@ static int wm_handler_operator_call(bContext *C, ListBase *handlers, wmEventHand
 					/* set cursor back to the default for the region */
 					wmWindow *win = CTX_wm_window(C);
 					WM_cursor_grab_disable(win, NULL);
-					ED_region_cursor_set(win, CTX_wm_area(C), CTX_wm_region(C));
+					ED_region_cursor_set(win, area, region);
 
 					BLI_remlink(handlers, handler);
 					wm_event_free_handler(handler);