Fix crash occuring with plugins in RGBFusion USB

Attempt to fix #4858 and #2662.

@mguimard found a related crash, but that crash seems to not be affected by the fix (unfortunately).

According to #2662 (comment 1054796174) , the zones vector in some threads is reported as uninitialized. This MR adds a size check to the method mentioned there (UpdateZoneLEDs()).

After further investigation, a recursive mutex was added throughout the entire controller, to prevent access to internal vectors while the structure is being changed. This won't help plugins that directly interact with the colors vector, but at least should cover most of the crashes.