update changelogs

Author: tstanmay13

fern/products/sdks/overview/java/changelog/2025-09-22.mdx

@@ -1,3 +1,7 @@
+## 3.5.7
+**`(fix):`** Fixed NullPointerException in builder setters when collections are null by adding null checks before addAll()/putAll() calls.
+
+
 ## 3.5.6
 **`(fix):`** Fixed wire test generation: paginated endpoints return `SyncPagingIterable<T>`, auth methods use correct builder patterns