bash: don't add leading $ if string is empty

[kxxt]

Hi,

Thanks for your nice work.

The leading $ is added even when the string is empty. We can actually drop the leading $ to make the output more beautiful in this special case.

• Output of my program before this change: env -C /home/kxxt $'\n'=134 LD_BIND_NOW=$'' LD_WARN=$'' LD_TRACE_LOADED_OBJECTS=1 LD_VERBOSE=$'' PWD=/home/kxxt SHLVL=3 _=/usr/lib64/ld-linux-x86-64.so.2 /usr/lib64/ld-linux-x86-64.so.2 /bin/true
• Output of my program after this change: env -C /home/kxxt $'\n'=134 LD_BIND_NOW='' LD_WARN='' LD_TRACE_LOADED_OBJECTS=1 LD_VERBOSE='' PWD=/home/kxxt SHLVL=3 _=/usr/lib64/ld-linux-x86-64.so.2 /usr/lib64/ld-linux-x86-64.so.2 /bin/true

[kxxt]

I'd change escape_prepare instead though; below is the diff I would like to merge. If you want to update your PR with that I'll merge it. Thank you for putting the energy in to doing this.

Thanks for your quick review. I have applied your diff.

[allenap]

Thanks! I've published 0.3.2 with this change.

Also, sorry, I meant to give you the diff, but I didn't strip out the leading commit stuff from it.