fixup! refactor: modernize array and string last element access using .at(-1)

Author: alan-agius4

packages/angular_devkit/core/src/utils/template.ts

@@ -253,7 +253,7 @@ function templateWithSourceMap(ast: TemplateAst, options?: TemplateOptions): str
     ]),
   );
 
-  const end = ast.children.length ? ast.children.at(-1)?.end : { line: 0, column: 0 };
+  const end = ast.children.at(-1)?.end ?? { line: 0, column: 0 };
   const nodes = ast.children
     .reduce((chunk, node) => {
       let code: string | SourceNode | (SourceNode | string)[] = '';