bug fix a segfault when closing a second X11 window, then resizing the first

ChangeLog

@@ -1,3 +1,11 @@
+2011-02-11  Robert Larice
+ * src/frontend/plotting/x11.c :
+    bug fix a segfault when closing a second x11-window, then resizing the first
+    copied a workaround from
+	2009-01-10 Holger Vogt
+	in windisp.c
+    FIXME, x11 structures and currentgraph ...
+
 2011-02-11  Robert Larice
  * src/frontend/parse-bison.c :
     and update the parser output

src/frontend/plotting/x11.c

@@ -881,6 +881,8 @@ killwin(Widget w, caddr_t client_data, caddr_t call_data)
     DEVDEP(graph).isopen = 0;
     /* MW. Not sure but DestroyGraph might free() to much - try Xt...() first */	
     XtDestroyWidget(DEVDEP(graph).shell);
+    if (graph == currentgraph)
+        currentgraph = FindGraph(graph->graphid - 1);
     DestroyGraph(graph->graphid);
 
 }