fix crash in time zone class - timezones without transitions were not handled correctly. Also a wrong exception type was thrown when time zone file did not have the expected magic.
fix crash in time zone class - timezones without transitions were not handled correctly.
Also a wrong exception type was thrown when time zone file did not have the expected magic.

maekitalo/cxxtools,maekitalo/cxxtools,maekitalo/cxxtools,maekitalo/cxxtools