SID - small bug in sid_envelope.sv

[LMN128]

'hold_zero' is written by both blocking and non-blocking assignments.
I think there (line 96) should be this:

if(state != ST_ATTACK && envelope == 1) hold_zero <= 1;

[sorgelig]

thanks for spotting it!
Functionally it has no difference, but may help the compiler. I've corrected it.