Fix mood reload.

Fix mood reload.

There was some confusion about how to determine whether the dummy mode
is currently active. At some places we tested if current_mood is NULL,
at others if current_mood->name is NULL. In fact neither check works:

	* if a playlist is open, current_mood is NULL (but the dummy
	mood is not loaded),

	* loading the dummy mood currently sets current_mood->name to
	"(dummy)".

This patch makes the latter variant the official one and fixes up
the code accordingly.

This also fixes the critical log message

	Jan 27 18:57:29 (5) (13487) afs_event: table moods, event 9: key not found in rbtree

which occured if the dummy mood was active while an event caused the
mood to be reloaded.