intel: Check for unsupported texture when finishing using as a render target

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=32541
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>

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

@@ -547,7 +547,8 @@ intel_finish_render_texture(struct gl_context * ctx,
        _glthread_GetID(), att->Texture->Name);
 
    /* Flag that this image may now be validated into the object's miptree. */
-   intel_image->used_as_render_target = GL_FALSE;
+   if (intel_image)
+      intel_image->used_as_render_target = GL_FALSE;
 
    /* Since we've (probably) rendered to the texture and will (likely) use
     * it in the texture domain later on in this batchbuffer, flush the