fix: init RoleHandler lazily to pass when RoleHandler is generated

[pvojtechovsky]

fix of #2063

[surli]

Thanks @pvojtechovsky for the fix! I just tried it with #2054 the test now works well, however the generated ModelRoleHandlers contains the following wrong imports:

import spoon.generating.meta.spoon.reflect.meta.impl.ListHandler;
import spoon.generating.meta.spoon.reflect.meta.impl.MapHandler;
import spoon.generating.meta.spoon.reflect.meta.impl.SetHandler;
import spoon.generating.meta.spoon.reflect.meta.impl.SingleHandler;

I had to remove them manually. I don't know if it's related with your changes here...

[pvojtechovsky]

I cannot imagine that this PR would cause the problems with import. I guess it is some other import related already merged PR.

[surli]

Ok I will open an issue then.