render/drm_format_set: fill dst in wlr_drm_format_set_copy

render/drm_format_set.c

@@ -162,6 +162,8 @@ bool wlr_drm_format_set_copy(struct wlr_drm_format_set *dst, const struct wlr_dr
 		out.len++;
 	}
 
+	*dst = out;
+
 	return true;
 }