Fixed migration error when non-null is not properly computed

Author: JanHolger

src/main/java/org/javawebstack/orm/TableInfo.java

@@ -256,7 +256,7 @@ public Object getDefault(String fieldName) {
 
     public boolean isNotNull(String fieldName) {
         if (idField.equals(fieldName))
-            return false;
+            return true;
         return false;
     }