fix(upgrade): fix empty transclusion content with AngularJS@>=1.5.8 (#22167)

The function provided by `ngUpgrade` as `parentBoundTranscludeFn` when
upgrading a component with transclusion, will break in AngularJS v1.5.8+
if no transclusion content is provided. The reason is that AngularJS
will try to destroy the transclusion scope (which would not be needed
any more). But since the transcluded content comes from Angular, not
AngularJS, there is no transclusion scope to destroy.
This commit fixes it by providing a dummy scope object with a no-op
`$destroy()` method.

Fixes #22175

PR Close #22167

Author: gkalpak

packages/upgrade/src/common/upgrade_helper.ts

@@ -122,9 +122,15 @@ export class UpgradeHelper {
   prepareTransclusion(): angular.ILinkFn|undefined {
     const transclude = this.directive.transclude;
     const contentChildNodes = this.extractChildNodes();
+    const attachChildrenFn: angular.ILinkFn = (scope, cloneAttachFn) => {
+      // Since AngularJS v1.5.8, `cloneAttachFn` will try to destroy the transclusion scope if
+      // `$template` is empty. Since the transcluded content comes from Angular, not AngularJS,
+      // there will be no transclusion scope here.
+      // Provide a dummy `scope.$destroy()` method to prevent `cloneAttachFn` from throwing.
+      scope = scope || {$destroy: () => undefined};
+      return cloneAttachFn !($template, scope);
+    };
     let $template = contentChildNodes;
-    let attachChildrenFn: angular.ILinkFn|undefined = (scope, cloneAttach) =>
-        cloneAttach !($template, scope);
 
     if (transclude) {
       const slots = Object.create(null);