Don't require TargetHandleType and TargetHandle to be present in requests
Don't require TargetHandleType and TargetHandle to be present in requests

The specification says that only ChannelType MUST be set. If the rest
makes no sense, the request should be rejected by the CM rather than
here.

This for example breaks group chats which have no TargetHandle or
TargetHandleType.

Reviewed-by: David Edmundson

TelepathyQt/telepathy-qt,tiagosh/telepathy-qt,freedesktop-unofficial-mirror/telepathy__telepathy-qt4,TelepathyIM/telepathy-qt,TelepathyIM/telepathy-qt,freedesktop-unofficial-mirror/telepathy__telepathy-qt4,freedesktop-unofficial-mirror/telepathy__telepathy-qt,tiagosh/telepathy-qt,tiagosh/telepathy-qt,TelepathyQt/telepathy-qt,freedesktop-unofficial-mirror/telepathy__telepathy-qt4,freedesktop-unofficial-mirror/telepathy__telepathy-qt,TelepathyQt/telepathy-qt,TelepathyIM/telepathy-qt,freedesktop-unofficial-mirror/telepathy__telepathy-qt4,freedesktop-unofficial-mirror/telepathy__telepathy-qt,TelepathyIM/telepathy-qt,tiagosh/telepathy-qt,TelepathyQt/telepathy-qt,TelepathyIM/telepathy-qt,freedesktop-unofficial-mirror/telepathy__telepathy-qt