fix: Do not log message when a field is not mapped on an identity pro…

…vider

Closes gravitee-io/issues#3016

gravitee-management-api-rest/src/main/java/io/gravitee/management/rest/resource/auth/OAuth2AuthenticationResource.java

@@ -336,7 +336,7 @@ private HashMap<String, String> getUserProfileAttrs(Map<String, String> userProf
             String field = entry.getKey();
             String mapping = entry.getValue();
 
-            if (mapping != null) {
+            if (mapping != null && !mapping.isEmpty()) {
                 try {
                     if (mapping.contains("{#")) {
                         map.put(field, templateEngine.convert(mapping));