[BUG] Double-mapping might cause crash

[djdiskmachine]

When mapping with mapping.xml, ControlRoom::Attach calls MultiChannelAdapter::AddChannel which in turn calls T_SimpleList::Insert
This has an assert for already existing items:
NAssert(!Contains(item)) ;

It seems a bit harsh to crash the application for events like this, consider changing for an if statement.

[MAPPING] Attached /event/b to key:0:s
[ERROR] Assertion failed: !Contains(item)
[ERROR] >> file [ion/T_SimpleList.cpp]
[ERROR] >> line 28
lgpt.deb-exe: /home/m/Documents/GitRepos/LittleGPTracker/projects/../sources/System/Console/n_assert.cpp:14: void __NAssert(const char*, const char*, unsigned int): Assertion `0' failed.
Aborted (core dumped)