WEB-826: Improve null-safety in ErrorHandlerInterceptor

Safely access response.error with optional chaining; honor root
error.defaultUserMessage before developerMessage. Handles network
errors and non-JSON responses without crashing.

Made-with: Cursor

Author: tkshsbcue

src/app/core/http/error-handler.interceptor.ts

@@ -45,11 +45,12 @@ export class ErrorHandlerInterceptor implements HttpInterceptor {
    */
   private handleError(response: HttpErrorResponse, request: HttpRequest<any>): Observable<HttpEvent<any>> {
     const status = response.status;
-    let errorMessage = response.error.developerMessage || response.message;
-    if (response.error.errors) {
-      if (response.error.errors[0]) {
-        errorMessage = response.error.errors[0].defaultUserMessage || response.error.errors[0].developerMessage;
-      }
+    const error = response?.error;
+    let errorMessage =
+      error?.defaultUserMessage || error?.developerMessage || response?.message || 'Unknown error';
+    if (error?.errors?.[0]) {
+      errorMessage =
+        error.errors[0].defaultUserMessage || error.errors[0].developerMessage || errorMessage;
     }
 
     const isClientImage404 = status === 404 && request.url.includes('/clients/') && request.url.includes('/images');