Fix remaining memory leak (GC :heap_line_num now flatlines)
Fix remaining memory leak (GC :heap_line_num now flatlines)

On reflection, I remember when I implemented the synth promise thing that
it was a bit of a quick hack - that'll teach me!
jweather/sonic-pi,jweather/sonic-pi,jweather/sonic-pi,jweather/sonic-pi,jweather/sonic-pi