Prevent segfault when reasonable configuration can not be found.

src/io_pipeline.c

@@ -609,6 +609,10 @@ update_state(MPPipeline *pipeline, const mp_state_io *new_state)
 void
 mp_io_pipeline_update_state(const mp_state_io *state)
 {
+	if (!pipeline) {
+		printf("no pipeline\n");
+		exit(1);
+	}
         mp_pipeline_invoke(pipeline,
                            (MPPipelineCallback)update_state,
                            state,