Fix fetchContainers if only one resource in container

src/frontend/packages/semantic-data-provider/src/dataProvider/utils/arrayOf.js

@@ -0,0 +1,14 @@
+const arrayOf = value => {
+  // If the field is null-ish, we suppose there are no values.
+  if (!value) {
+    return [];
+  }
+  // Return as is.
+  if (Array.isArray(value)) {
+    return value;
+  }
+  // Single value is made an array.
+  return [value];
+};
+
+export default arrayOf;

src/frontend/packages/semantic-data-provider/src/dataProvider/utils/fetchContainers.js

@@ -1,5 +1,6 @@
 import jsonld from 'jsonld';
 import isobject from 'isobject';
+import arrayOf from './arrayOf';
 
 export const isType = (type, resource) => {
   const resourceType = resource.type || resource['@type'];
@@ -30,7 +31,7 @@ const fetchContainers = async (containers, resourceId, params, config) => {
       })
       .then(json => {
         if (isType('ldp:Container', json)) {
-          return json['ldp:contains'].map(resource => ({ '@context': json['@context'], ...resource }));
+          return arrayOf(json['ldp:contains']).map(resource => ({ '@context': json['@context'], ...resource }));
         }
         throw new Error(`${containerUri} is not a LDP container`);
       })