Setting an ill-formatted Time-ish String into a TimeZone aware column raises an ArgumentError

Giving a `Date._parse`able but invalid DateTime-ish String value into a TimeZone aware AR column immediately raises since 4.0.x.

This regression was caused by 41ff6a10216f48f43605a1f9cd6094765cab750f which stopped rescuing errors when parsing.

This patch brings back the AR3 behaviour that sets nil in such case instead of raising.
/cc @pixeltrix