Fix - Existing custom properties getting removed on import of empty e…

…xtension column (#19234)

openmetadata-service/src/main/java/org/openmetadata/service/jdbi3/EntityRepository.java

@@ -2822,6 +2822,13 @@ private void updateExtension() {
         return;
       }
 
+      if (operation == Operation.PUT && updatedExtension == null) {
+        // Revert change to non-empty extension if it is being updated by a PUT request
+        // For PUT operations, existing extension can't be removed.
+        updated.setExtension(origExtension);
+        return;
+      }
+
       List<JsonNode> added = new ArrayList<>();
       List<JsonNode> deleted = new ArrayList<>();
       JsonNode origFields = JsonUtils.valueToTree(origExtension);