core/library: Close directory after reading

We were opening a directory for scanning, but we never closed when we
were done.  If we do this enough then the kernel starts telling us that
there are too many open files.

Signed-off-by: Anna Schumaker <Anna@OcarinaProject.net>

core/library.cpp

@@ -119,6 +119,7 @@ static void scan_path(void *data)
 	}
 
 	track_db_commit();
+	g_dir_close(dir);
 	delete scan;
 }