fix(angular): migration of browserTarget to buildTarget should handle…

… empty config #26681 (#26690)

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## Current Behavior
<!-- This is the behavior we have today -->
The migration from `browserTarget` to `buildTarget` assumed config would
not be undefined.


## Expected Behavior
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-->
The migration should check if config is undefined

## Related Issue(s)
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merged. -->

Fixes #26681

packages/angular/src/migrations/update-17-1-0/browser-target-to-build-target.ts

@@ -67,7 +67,7 @@ function updateConfig(config: {
   browserTarget?: string;
   buildTarget?: string;
 }): void {
-  if (config.browserTarget) {
+  if (config && config.browserTarget) {
     config.buildTarget ??= config.browserTarget;
     delete config.browserTarget;
   }