add error if no layer added to a basemap

src/views/project/Project_mapping.vue

@@ -86,9 +86,13 @@ export default {
     checkTitles() {
       let isValid = true;
       this.basemaps.forEach((basemap) => {
+        console.log(basemap);
         if (basemap.title === null || basemap.title === "") {
           basemap.errors = "Veuillez compléter ce champ.";
           isValid = false;
+        } else if (basemap.layers.length === 0) {
+          basemap.errors = "Veuillez ajouter au moins un layer.";
+          isValid = false;
         } else {
           basemap.errors = "";
         }