[fix] RubyException#toJava(Object) shouldn't return null #5488
... a regression since the exception hierarchy rewrite in 9.2 spotted at: sparklemotion/nokogiri#1818 for compat `rubyException.toJava(Object.class)` shall return self
NOTE: no strong opinions against changing the behaviour of
this PR simply restores pre 9.2 ... with the new exception hierarchy it might make sense to convert by default. most Java convertable types do the coercion e.g.