Fixed crash in wglShareList.

dlls/opengl32/wgl.c

@@ -560,7 +560,7 @@ BOOL WINAPI wglShareLists(HGLRC hglrc1,
 
   TRACE("(%p, %p)\n", org, dest);
 
-  if (dest->ctx != NULL) {
+  if (NULL != dest && dest->ctx != NULL) {
     ERR("Could not share display lists, context already created !\n");
     return FALSE;
   } else {
@@ -570,15 +570,16 @@ BOOL WINAPI wglShareLists(HGLRC hglrc1,
       LEAVE_GL();
       TRACE(" created a delayed OpenGL context (%p) for Wine context %p\n", org->ctx, org);
     }
-
+    if (NULL != dest) {
       ENTER_GL();
       /* Create the destination context with display lists shared */
       dest->ctx = glXCreateContext(org->display, dest->vis, org->ctx, True);
       LEAVE_GL();
       TRACE(" created a delayed OpenGL context (%p) for Wine context %p sharing lists with OpenGL ctx %p\n", dest->ctx, dest, org->ctx);
-  }
-
       return TRUE;
+    }
+  }
+  return FALSE;
 }
 
 /***********************************************************************