(core) Refactor disabled summary button logic

Summary:
A project test began failing because of an incompatibility with pointer-events
being disabled. This gets us back to green.

Test Plan: Existing tests.

Reviewers: jordigh

Reviewed By: jordigh

Subscribers: jordigh

Differential Revision: https://phab.getgrist.com/D4325

app/client/ui/PageWidgetPicker.ts

@@ -328,6 +328,8 @@ export class PageWidgetSelect extends Disposable {
   private _isNewTableDisabled = Computed.create(this, this._value.type, (use, type) => !isValidSelection(
     'New Table', type, {isNewPage: this._options.isNewPage, summarize: use(this._value.summarize)}));
 
+  private _isSummaryDisabled = Computed.create(this, this._value.type, (_use, type) => !isSummaryCompatible(type));
+
   constructor(
     private _value: IWidgetValueObs,
     private _tables: Observable<TableRec[]>,
@@ -389,8 +391,9 @@ export class PageWidgetSelect extends Disposable {
                   cssEntry.cls('-selected', (use) => use(this._value.summarize) &&
                                                      use(this._value.table) === table.id()
                   ),
-                  cssEntry.cls('-disabled', (use) => !isSummaryCompatible(use(this._value.type))),
+                  cssEntry.cls('-disabled', this._isSummaryDisabled),
-                  dom.on('click', (ev, el) => this._selectPivot(table.id(), el as HTMLElement)),
+                  dom.on('click', (_ev, el) =>
+                    !this._isSummaryDisabled.get() && this._selectPivot(table.id(), el as HTMLElement)),
                   testId('pivot'),
               ),
               testId('table'),
@@ -572,7 +575,6 @@ const cssEntry = styled('div', `
   &-disabled {
     color: ${theme.widgetPickerItemDisabledBg};
     cursor: default;
-    pointer-events: none;
   }
   &-disabled&-selected {
     background-color: inherit;