[ticket/17365] Prevent keyword limit being bypassed with the use of +, - and |
Provided `$countable_keywords` wherein the existing `$keywords` value is
modified so that any `-`, `+` and `|` characters without preceding spaces
is replaced with the same but with a space in front of each.
These spaces allow the string to be more accurately split when used instead
of $keywords inside the $num_keywords calculation.
This prevents the word limit being bypassed in search by the use of
operators without whitespace.
