Fix crashes on 'Format value'

[nipsufn]

Puddletag kept crashing when trying to select "Format Value" (Actions -> Actions / Quick Actions -> Add / Edit -> Add function -> Format Value).
Proposed PR appears to fix the issue.

Traceback (most recent call last):
File "/usr/lib/python3.10/site-packages/puddlestuff/actiondlg.py", line 364, in showexample
val = apply_actions([self.func], audio, state, fields)
File "/usr/lib/python3.10/site-packages/puddlestuff/findfunc.py", line 620, in apply_actions
temp = func.runFunction(val, audio, state, None, r_tags)
File "/usr/lib/python3.10/site-packages/puddlestuff/findfunc.py", line 870, in runFunction
return func(**topass)
File "/usr/lib/python3.10/site-packages/puddlestuff/functions.py", line 204, in formatValue
ret = findfunc.parsefunc(p_pattern, m_tags, state=state)
File "/usr/lib/python3.10/site-packages/puddlestuff/findfunc.py", line 462, in parsefunc
func_parsed = run_format_func(func[0], func[1:], m_audio, s_audio, state=state, extra=extra)
File "/usr/lib/python3.10/site-packages/puddlestuff/findfunc.py", line 328, in run_format_func
message = message.arg(arglen_error(e, topass, func, False))
File "/usr/lib/python3.10/site-packages/puddlestuff/findfunc.py", line 71, in arglen_error
raise e
File "/usr/lib/python3.10/site-packages/puddlestuff/findfunc.py", line 322, in run_format_func
ret = func(**topass)
TypeError: replaceWithReg() missing 1 required positional argument: 'repl'
[1] 4305 IOT instruction (core dumped) puddletag -d

[sandrotosi]

thanks @nipsufn !