Resolve "crash in SBA decoder with some inputs"

Closes #694 (closed)

[x] The crash occurs due to computation of log(0) by BASOP_Util_Log2, which was not handled in the EVS implemented scalebands().
[x] Created a separate copy of scalebands() as scalebands_fx() for IVAS path because after making the change in EVS function, many streams got bit-inexact in decoder and encoder for EVS bit-exact testing.