[EDataCalView] Ensure GDBus string for view signals
[EDataCalView] Ensure GDBus string for view signals

Make sure the string passed to GDBus calls (and signals) is valid
UTF-8 string, otherwise GVariant claims runtime warning and other
things get broken.

matzipan/evolution-data-server,matzipan/evolution-data-server,matzipan/evolution-data-server,tintou/evolution-data-server,tintou/evolution-data-server,matzipan/evolution-data-server,tintou/evolution-data-server,tintou/evolution-data-server,matzipan/evolution-data-server