Room::downloadFile(): make sure to store the initiated file transfer anew
Room::downloadFile(): make sure to store the initiated file transfer anew

QHash doesn't overwrite an entry if it already exists; this might lead to the target file name from the previous transfer kept in the table of file transfers. The commit fixes that.

QMatrixClient/libqmatrixclient,QMatrixClient/libqmatrixclient,Fxrh/libqmatrixclient