intel: Don't segfault on TFP from a bad drawable.

src/mesa/drivers/dri/intel/intel_context.c

@@ -233,6 +233,9 @@ intel_update_renderbuffers(__DRIcontext *context, __DRIdrawable *drawable)
 						&count,
 						drawable->loaderPrivate);
 
+   if (buffers == NULL)
+      return;
+
    drawable->x = 0;
    drawable->y = 0;
    drawable->backX = 0;

src/mesa/drivers/dri/intel/intel_tex_image.c

@@ -733,6 +733,12 @@ intelSetTexBuffer(__DRIcontext *pDRICtx, GLint target, __DRIdrawable *dPriv)
    intel_update_renderbuffers(pDRICtx, dPriv);
 
    rb = intel_fb->color_rb[0];
+   /* If the region isn't set, then intel_update_renderbuffers was unable
+    * to get the buffers for the drawable.
+    */
+   if (rb->region == NULL)
+      return;
+
    type = GL_BGRA;
    format = GL_UNSIGNED_BYTE;
    internalFormat = (rb->region->cpp == 3 ? 3 : 4);