glx: Catch another failure case in drawable creation

Reviewed-by: Eric Anholt <eric@anholt.net>
Signed-off-by: Adam Jackson <ajax@redhat.com>

glx/glxcmds.c

@@ -515,6 +515,10 @@ __glXGetDrawable(__GLXcontext * glxc, GLXDrawable drawId, ClientPtr client,
                                                 pDraw, drawId,
                                                 GLX_DRAWABLE_WINDOW,
                                                 drawId, glxc->config);
+    if (!pGlxDraw) {
+	*error = BadAlloc;
+	return NULL;
+    }
 
     /* since we are creating the drawablePrivate, drawId should be new */
     if (!AddResource(drawId, __glXDrawableRes, pGlxDraw)) {