jf_activity: fix infinite load

computeScrollInfo wasn't being called before the first detectScroll
call, because there is no search functionality (somehow, i think). Fixed
by calling it if _scroll.rowHeight is 0.

ts/modules/accounts.ts

@@ -2952,6 +2952,7 @@ class UserInfo extends PaginatedList {
                 }
 
                 this._search.setOrdering(Array.from(this.entries.keys()), "Date", true);
+                this.computeScrollInfo();
             },
             replaceWithNewItems: (resp: PaginatedDTO) => {
                 let entriesOnDOM = new Map<string, boolean>();