osc: fix runtime enable_osc(true/false)

There were few issues:
- When it's disabled and then enabled, it was displaying the osc briefly and
  then autohide right away. Don't do that.
- When it's enabled and then disabled, it was not removing the osc from screen
  if called while the osc is visible (because tick() is responsible for the hide
  but it doesn't render() the empty osc when the osc is disabled).
- Due to delayed/async unbinding of mouse events it was possible to show_osc()
  after it got disabled e.g. from mouse_move. Prevent this.

player/lua/osc.lua

@@ -1607,6 +1607,9 @@ end
 
 
 function show_osc()
+    -- show when disabled can happen (e.g. mouse_move) due to async/delayed unbinding
+    if not state.enabled then return end
+
     msg.debug("show_osc")
     --remember last time of invocation (mouse move)
     state.showtime = mp.get_time()
@@ -1616,12 +1619,17 @@ function show_osc()
     if (user_opts.fadeduration > 0) then
         state.anitype = nil
     end
-
 end
 
 function hide_osc()
     msg.debug("hide_osc")
-    if (user_opts.fadeduration > 0) then
+    if not state.enabled then
+        -- typically hide happens at render() from tick(), but now tick() is
+        -- no-op and won't render again to remove the osc, so do that manually.
+        state.osc_visible = false
+        timer_stop()
+        render() -- state.osc_visible == false -> remove the osc from screen
+    elseif (user_opts.fadeduration > 0) then
         if not(state.osc_visible == false) then
             state.anitype = "out"
             control_timer()
@@ -1958,9 +1966,8 @@ function enable_osc(enable)
     state.enabled = enable
     if enable then
         do_enable_keybindings()
-        show_osc()
     else
-        hide_osc()
+        hide_osc() -- acts immediately when state.enabled == false
         if state.showhide_enabled then
             mp.disable_key_bindings("showhide")
         end