ticket:11007 Improved checking for NULL time zones in calendar code.

git-svn-id: http://source.icu-project.org/repos/icu/icu/trunk/source@36025 251d0590-4201-4cf1-90de-194747b24ca1
ticket:10966: Fix NumberFormat::createInstance to return U_MISSING_RESOURCE_ERROR when there is missing resource data.

git-svn-id: http://source.icu-project.org/repos/icu/icu/trunk/source@36026 251d0590-4201-4cf1-90de-194747b24ca1