Retrieving timezone offset of Asia/Tokyo fails

[Takashi Kato]

This raises an error.

(import (sagittarius timezone))
(timezone-offset (timezone "Asia/Tokyo"))

[Takashi Kato]

This is rather but on TZ database. The rule "Japan" contains 4 rules but none of them indicates later than 1951. So find-rule can't find a rule of current time. Not sure if there's other timezone which has the same situation so might be safer to return default rule instead of raising an error when there's no rule found.

[Takashi Kato]

Returning #f instread of raising an error when timezone rule wasn't found (Fixes #150)

→ <<cset 5d4c944d6b15>>