fix disable/re-enable text/color on button on accounts

account-disabled-ness was/is derived from a class on the badge in the
account's row, which after a UI change was removed. Now depends on the
correct (and more likely to remain throughout changes) "hidden" class.

For #370.

ts/modules/accounts.ts

@@ -132,7 +132,7 @@ class user implements User, SearchableItem {
         }
     }
 
-    get disabled(): boolean { return this._disabled.classList.contains("chip"); }
+    get disabled(): boolean { return !(this._disabled.classList.contains("hidden")); }
     set disabled(state: boolean) {
         if (state) {
             this._disabled.classList.remove("hidden")