Fix display caption loading track: event based now

src/mpv_control.py

@@ -65,12 +65,11 @@ def osd_observer(_name, value):
         print_there(0, 0, '\r'+osd_string[:term_len])
 
 
-@player.property_observer('stream-open-filename')
+@player.event_callback('start-file')
 @logger.catch
-def waiting_load_observer(_name, value):
+def starting_file_handler(value):
     '''just show loading state'''
-    if value and player.core_idle:
-        print_there(0, 0, '\rLoading track...')
+    print_there(0, 0, '\rLoading track...')
 
 
 @player.property_observer('percent-pos')