crash on start when using clock format %c

[thugcee]

To reproduce:

clone repo, compile, change example config from:

[time]
  id clock
  timeout 5
  format %T
shell bg.sh

to:

[time]
  id clock
  timeout 5
  format %c

and start tint3 with this config to get
Segmentation fault
OR
*** Error in `./tint3': munmap_chunk(): invalid pointer: 0x0000000001db8d90 ***,
OR
double mem free error

Locale is pl_PL.utf8. With LC_ALL=C it starts, but there is some text corruption in clock.

[tmathmeyer]

fixed in the latest commit. thanks for finding this!