Return false if can't seek in MPRIS plugin, a string is actually not a boolean.

awainzin--;

src/libtomahawk/infosystem/infoplugins/unix/mprisplugin.cpp

@@ -191,7 +191,7 @@ MprisPlugin::canSeek() const
 {
     PlaylistInterface *p = AudioEngine::instance()->playlist();
     if (!p)
-        return "None";
+        return false;
     return p->seekRestrictions() != PlaylistInterface::NoSeek;
 
 }