rpi: Remove dangling reference to weston_view

This also marks the rpir_view for destroy in rpi_renderer_finish_frame()
diff --git a/src/rpi-renderer.c b/src/rpi-renderer.c
index 812e6e7..7f79410 100644
--- a/src/rpi-renderer.c
+++ b/src/rpi-renderer.c
@@ -1501,6 +1501,8 @@
 	if (!view)
 		return;
 
+	view->view = NULL;
+
 	/* If guaranteed to not be on screen, just detroy it. */
 	if (wl_list_empty(&view->link))
 		rpir_view_destroy(view);