WebSearch: fix get_fieldvalues() when recid is str

• recid might be string, so try to convert it to int in the get_fieldvalues function (needed for WebSubmit, major user of this function, which calls it in many different places with a string argument instead of int).

• Note: this was committed previously in 705bb7160ce9691967b1504b28f230917c69149a but it was apparently dropped by mishap later.