BUG/MAJOR: map: fix a segfault when using http-request set-map

The bug happens with an existing entry, when you try to overwrite the
value with wrong data, for example, a string when the type is INT.

The code path was not secure and tried to set *err and *merr while
err = merr = NULL when performing an http action.

Must be backported in 1.6, 1.7, 1.8.
1 file changed