fix: return value

Co-authored-by: Shiwei Zhang <shizh@microsoft.com>
Signed-off-by: Kyle Tarplee <kmtarplee@ieee.org>

registry/remote/auth/cache.go

@@ -205,7 +205,7 @@ func (fc *fallbackCache) GetToken(ctx context.Context, registry string, scheme S
 func (fc *fallbackCache) Set(ctx context.Context, registry string, scheme Scheme, key string, fetch func(context.Context) (string, error)) (string, error) {
 	token, err := fc.primary.Set(ctx, registry, scheme, key, fetch)
 	if err != nil {
-		return token, err
+		return "", err
 	}
 
 	return fc.secondary.Set(ctx, registry, scheme, key, func(ctx context.Context) (string, error) {