fix: prevent browser caching of API responses in MetadataInterceptor

Author: boojack

server/router/api/v1/connect_interceptors.go

@@ -56,7 +56,7 @@ func (*MetadataInterceptor) WrapUnary(next connect.UnaryFunc) connect.UnaryFunc
 
 		// Prevent browser caching of API responses to avoid stale data issues
 		// See: https://github.com/usememos/memos/issues/5470
-		if resp != nil {
+		if resp != nil && resp.Header() != nil {
 			resp.Header().Set("Cache-Control", "no-cache, no-store, must-revalidate")
 			resp.Header().Set("Pragma", "no-cache")
 			resp.Header().Set("Expires", "0")