CAMEL-13981: make sure that the property helper...
... class is generated
The helper class would be generated if the `last` boolean flag was set
and the conditions in the helper did not prevent further execution of
the `processModelClass` method.
For example if the last processed element is abstract, and it might be
depending on the order of the elements in the `Set` of processed
elements the `DefinitionPropertiesPlaceholderProviderHelper.java` would
not be generated.
