return default value when property doesn't exist

Signed-off-by: Marlon Pina Tojal <marlont@backbase.com>

src/main/java/org/dependencytrack/persistence/QueryManager.java

@@ -1236,6 +1236,8 @@ public boolean isEnabled(final ConfigPropertyConstants configPropertyConstants)
         );
         if (property != null && ConfigProperty.PropertyType.BOOLEAN == property.getPropertyType()) {
             return BooleanUtil.valueOf(property.getPropertyValue());
+        } else if (property == null) {
+            return BooleanUtil.valueOf(configPropertyConstants.getDefaultPropertyValue());
         }
         return false;
     }