When attempting to perform a NOT LIKE (or != with a long value) on a
single-value CF, the search is limited by:

  Content NOT LIKE '%value%' OR
  ((Content = '' OR Content IS NULL) AND LargeContent NOT LIKE '%value%')

However, it must also be open to the possibility that the ticket did not
contain a value for that CF, which is a valid method of having
not-that-value.  It thus also added the possibility for lack-of-value by
further limiting by:

   OR Content IS NULL

Unfortunately, as Content is nearly definitionally NULL for rows with
LargeContent, this results in a false positives where LargeContent
matches '%value%' and thus the ticket should not match.

The limitation of "or the ticket could fail to have a value for the CF"
is better stated by checking that OCFV.id IS NULL, rather than
OCFV.Content IS NULL; switch to this to avoid the false positive.  Note
that $column cannot be defined at this point, as it has previously been
checked for truth, and return'd already in such cases, so the removing
the reference to $column is intentional.