fix(compiler): handle undefined annotation metadata (#23349)

In certain cases seen in production, simplify() can returned
undefined when simplifying decorator metadata. This has proven tricky
to reproduce in an isolated test, but the fix is simple and low-risk:
don't attempt to spread an undefined set of annotations in the first
place.

PR Close #23349

Author: alxhub

packages/compiler/src/aot/static_reflector.ts

@@ -163,7 +163,9 @@ export class StaticReflector implements CompileReflector {
       let ownAnnotations: any[] = [];
       if (classMetadata['decorators']) {
         ownAnnotations = simplify(type, classMetadata['decorators']);
-        annotations.push(...ownAnnotations);
+        if (ownAnnotations) {
+          annotations.push(...ownAnnotations);
+        }
       }
       if (parentType && !this.summaryResolver.isLibraryFile(type.filePath) &&
           this.summaryResolver.isLibraryFile(parentType.filePath)) {