fix usage of method

src/client/js/app.jsx

@@ -123,7 +123,7 @@ if (pageContainer.state.pageId != null) {
   });
 
   // show the Page accessory modal when query of "compare" is requested
-  if (revisionComparerContainer.getRevisionIDsToCompareAsParam.length > 0) {
+  if (revisionComparerContainer.getRevisionIDsToCompareAsParam().length > 0) {
     pageAccessoriesContainer.openPageAccessoriesModal('pageHistory');
   }
 }

src/client/js/services/RevisionComparerContainer.js

@@ -44,7 +44,7 @@ export default class RevisionComparerContainer extends Container {
   async initRevisions() {
     const latestRevision = await this.fetchLatestRevision();
 
-    const [sourceRevisionId, targetRevisionId] = this.getRevisionIDsToCompareAsParam;
+    const [sourceRevisionId, targetRevisionId] = this.getRevisionIDsToCompareAsParam();
     const sourceRevision = sourceRevisionId ? await this.fetchRevision(sourceRevisionId) : latestRevision;
     const targetRevision = targetRevisionId ? await this.fetchRevision(targetRevisionId) : latestRevision;
     const compareWithLatest = targetRevisionId ? false : this.state.compareWithLatest;