glx:dri_common.c: check psc->driScreen->createDrawable return value

createDrawable may return NULL value, we should check it, or it will
make a segment failed.

[minor-indent-issue-fixed-by: Yuanhan Liu]

Signed-off-by: Wang YanQing <udknight@gmail.com>
Reviewed-by: Yuanhan Liu <yuanhan.liu@linux.intel.com>

src/glx/dri_common.c

@@ -403,6 +403,12 @@ driFetchDrawable(struct glx_context *gc, GLXDrawable glxDrawable)
 
    pdraw = psc->driScreen->createDrawable(psc, glxDrawable,
                                           glxDrawable, gc->config);
+
+   if (pdraw == NULL) {
+      ErrorMessageF("failed to create drawable\n");
+      return NULL;
+   }
+
    if (__glxHashInsert(priv->drawHash, glxDrawable, pdraw)) {
       (*pdraw->destroyDrawable) (pdraw);
       return NULL;