Improve the displayName udpate message to avoid having "(null)"
Improve the displayName udpate message to avoid having "(null)"

matrix-org/matrix-ios-console,vector-im/riot-ios,matrix-org/matrix-ios-console,vector-im/riot-ios,vector-im/riot-ios,vector-im/riot-ios,vector-im/vector-ios,vector-im/riot-ios,vector-im/riot-ios,vector-im/vector-ios,vector-im/vector-ios