This is probably still a bug, or a difficult to understand "feature" of the xotcl object initialization.
The variable $parameter_obj gets set to the initial value of "". It should probably remain unset until explicitly defined, or the error should somehow expose which parameter object was not found.
For instance, you could use:
if {[info proc $parameter_obj] ne "$parameter_obj"} {
return -code error "Parameter object proc dne, maybe restart server."
}
$parameter_obj ...
