fix(core): fix client crash (#12966)

<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->

## Summary by CodeRabbit

* **Bug Fixes**
* Improved reliability when displaying OAuth provider icons by handling
cases where the provider may not be recognized, preventing potential
errors during authentication.

<!-- end of auto-generated comment: release notes by coderabbit.ai -->

packages/frontend/core/src/components/affine/auth/oauth.tsx

@@ -110,7 +110,10 @@ interface OauthProviderProps {
 }
 
 function OAuthProvider({ onContinue, provider }: OauthProviderProps) {
-  const { icon } = OAuthProviderMap[provider];
+  const { icon } =
+    provider in OAuthProviderMap
+      ? OAuthProviderMap[provider]
+      : { icon: undefined };
 
   const onClick = useCallback(() => {
     onContinue(provider);