Fix segfault in sccp_pbx_channel_allocate (Reported by Alena Juk)

git-svn-id: https://svn.code.sf.net/p/chan-sccp-b/code/trunk@5385 43c1dc8c-776e-4df2-8ef1-6e829299be21
Update ChangeLog

git-svn-id: https://svn.code.sf.net/p/chan-sccp-b/code/trunk@5386 43c1dc8c-776e-4df2-8ef1-6e829299be21