Insteon: success_callback crash on PLM link

[pmatis]

I just received a box full of more Insteon devices, and I'm starting to
link them to the PLM. I choose "Initiate linking as controller" the hold
the set button on the new device. It beeps and all is ok, except:

Can't call method "success_callback" on an undefined value at
/opt/misterhouse/bin/../lib/Insteon_PLM.pm line 772.
at mh line 31
main::ANON('Can't call method "success_callback" on an
undefined value a...') called at
/opt/misterhouse/bin/../lib/Insteon_PLM.pm line 772
Insteon_PLM::parse_data('Insteon_PLM=HASH(0x6371db0)',
'0253010014cfeb012e41025014cfeb223e') called at
/opt/misterhouse/bin/../lib/Insteon_PLM.pm line 204
Insteon_PLM::check_for_data('Insteon_PLM=HASH(0x6371db0)') called at
/opt/misterhouse/bin/../lib/Insteon/BaseInterface.pm line 33
Insteon::BaseInterface::check_for_data() called at mh line 1409
main::run_hooks('MainLoop_pre') called at (eval 336) line 5
main::MainLoop_pre_hooks() called at mh line 1522
main::check_for_action called at mh line 3303
main::monitor_commands called at mh line 6724
mh rc=2
mh had an unexpected exit ... sleep a bit, then restarting

[krkeegan]

Oops, looks like I solved part of this in #324 with the same solution, the second part in the PLM was not merged though