Remove no longer needed try{} block in related rel instantiation

Remove no longer needed try{} block in related rel instantiation

This try{} is no longer necessary after 3b4c4d72, but was missed due its
function not being readily apparent. The only known case where this
exception could be raised and be silenced is if an uninserted object had
some filter relations populated directly via {_inflated_column} *before*
related_resultset() has ever been called. This would result in a cascade
of failures during the relationship resolution, and bubble up here.

Starting with 3b4c4d72 the empty related resultset is instantiated ahead
of time, and everything works properly from there on.

In the unlikely case this does cause issues downstream, a way will be
found to address this ( worst case scenario by reintroducing the try{} )