compositor-x11: fix segfault when use_pixman is true

Signed-off-by: Ryo Munakata <ryomnktml@gmail.com>
Reviewed-by: Daniel Stone <daniels@collabora.com>

libweston/compositor-x11.c

@@ -917,8 +917,9 @@ x11_output_enable(struct weston_output *base)
 			weston_log("Failed to create pixman renderer for output\n");
 			x11_output_deinit_shm(b, output);
 			goto err;
-		output->base.repaint = x11_output_repaint_shm;
 		}
+
+		output->base.repaint = x11_output_repaint_shm;
 	} else {
 		/* eglCreatePlatformWindowSurfaceEXT takes a Window*
 		 * but eglCreateWindowSurface takes a Window. */