[coverity] Avoid a buffer-overrun.
[coverity] Avoid a buffer-overrun.

'escape_index' is ensured to be less than 'sizeof(escape_buffer)-1'.
This guarantees enough space for one more character in the
escape_buffer. However, if we meet this condition, we go ahead and shove
a character and a null-terminator in to the string, potentially leading
to a buffer overrun.

acleasby/lnav,acleasby/lnav,tstack/lnav,sureshsundriyal/lnav,tstack/lnav,sureshsundriyal/lnav,sureshsundriyal/lnav,sureshsundriyal/lnav,acleasby/lnav,acleasby/lnav,acleasby/lnav,tstack/lnav,tstack/lnav