xdg-shell: check for existing role before setting xdg_popup_surface_role

Hopefully fixes #2056

types/xdg_shell/wlr_xdg_popup.c

@@ -288,11 +288,6 @@ void create_xdg_popup(struct wlr_xdg_surface *xdg_surface,
 		return;
 	}
 
-	if (!wlr_surface_set_role(xdg_surface->surface, &xdg_popup_surface_role,
-			xdg_surface, xdg_surface->resource, XDG_WM_BASE_ERROR_ROLE)) {
-		return;
-	}
-
 	if (xdg_surface->role != WLR_XDG_SURFACE_ROLE_NONE) {
 		wl_resource_post_error(xdg_surface->resource,
 			XDG_SURFACE_ERROR_ALREADY_CONSTRUCTED,
@@ -300,6 +295,11 @@ void create_xdg_popup(struct wlr_xdg_surface *xdg_surface,
 		return;
 	}
 
+	if (!wlr_surface_set_role(xdg_surface->surface, &xdg_popup_surface_role,
+			xdg_surface, xdg_surface->resource, XDG_WM_BASE_ERROR_ROLE)) {
+		return;
+	}
+
 	assert(xdg_surface->popup == NULL);
 	xdg_surface->popup = calloc(1, sizeof(struct wlr_xdg_popup));
 	if (!xdg_surface->popup) {