Fix object type custom attribute definition cache
Fix object type custom attribute definition cache

The custom attribute definitions that are for the object type and not
for one specific object, do not have a definition_id. That is why None
must be present in the cache.

VinnieJohns/ggrc-core,kr41/ggrc-core,plamut/ggrc-core,plamut/ggrc-core,j0gurt/ggrc-core,VinnieJohns/ggrc-core,edofic/ggrc-core,selahssea/ggrc-core,j0gurt/ggrc-core,plamut/ggrc-core,kr41/ggrc-core,andrei-karalionak/ggrc-core,VinnieJohns/ggrc-core,AleksNeStu/ggrc-core,josthkko/ggrc-core,edofic/ggrc-core,selahssea/ggrc-core,josthkko/ggrc-core,AleksNeStu/ggrc-core,andrei-karalionak/ggrc-core,josthkko/ggrc-core,VinnieJohns/ggrc-core,j0gurt/ggrc-core,plamut/ggrc-core,AleksNeStu/ggrc-core,josthkko/ggrc-core,AleksNeStu/ggrc-core,kr41/ggrc-core,andrei-karalionak/ggrc-core,selahssea/ggrc-core,edofic/ggrc-core,j0gurt/ggrc-core,andrei-karalionak/ggrc-core,edofic/ggrc-core,kr41/ggrc-core,selahssea/ggrc-core