0 RR groups

[d.healey]

Develop branch:

When I drag in some samples and map them using the file name token parser I get this:

Even if I'm mapping to multiple RR groups. If I click ok I get a blank mapping editor with no samples mapped, if I click cancel I also get a blank mapping editor.

[d.healey]

Little more info on this, I ran the debug build and get this (for every sample file) in the terminal when the issue occurs:

JUCE Assertion failure in LockHelpers.cpp:76

[Christoph Hart]

I fixed a few sampler related issues, but oh boy, there's quite something to do :)

I rewrote the sample handling to support full undo for every sample editing operation including adding / removing samples, but things might have gotten a bit glitchy...

[d.healey]

@christoph-hart I will report all glitches I find :)