Improve ng2 error handler.

Author: schinkentanz

lib/angular2/shared/services/core/error.ejs

@@ -8,6 +8,13 @@ import { Observable, throwError } from 'rxjs';
 @Injectable()
 export class ErrorHandler {
   public handleError(errorResponse: HttpErrorResponse): Observable<never> {
-    return throwError(errorResponse.error.error || 'Server error');
+    if (errorResponse instanceof Error) {
+      return throwError(errorResponse);
+    }
+
+    const error = errorResponse?.error?.error;
+    const errorMessage = error?.message || error?.stack || error || 'Unknown error occured';
+
+    return throwError(new Error(errorMessage));
   }
 }