Added some fixes from people, and updated Changelog about this.

ChangeLog

@@ -29,6 +29,10 @@ Changes since version 0.52.0:
 - fixed crash with InfoPanel in multihead dpy
 - Fixed bug in WPrefs that added a new line at the end of autostart script
   at every save, growing it indefinitely.
+- fixed a memory leak in wrlib (Wolfram Gloger <wmglo@dent.med.uni-muenchen.de>)
+- fixed crash during forced shutdown of X (Wolfram Gloger
+					   <wmglo@dent.med.uni-muenchen.de>)
+
 
 Changes since version 0.51.2:
 .............................

src/actions.c

@@ -928,7 +928,8 @@ wIconifyWindow(WWindow *wwin)
 	wwin->icon = wIconCreate(wwin);
     }
 
-    wwin->icon->mapped = 1;
+    if (wwin->icon)
+        wwin->icon->mapped = 1;
     wwin->flags.miniaturized = 1;
     wwin->flags.mapped = 0;
 

src/startup.c

@@ -203,7 +203,7 @@ catchXError(Display *dpy, XErrorEvent *error)
  *---------------------------------------------------------------------- 
  */
 static int
-handleXIO(Display *dpy)
+handleXIO(Display *xio_dpy)
 {
     dpy = NULL;
     Exit(0);