osc.lua: avoid infinite ticks loop on idle

Before this commit, animation-end was handled at render(), however,
it's not called on idle, which resulted in state.anitype ~= nil, with
nothing to reset it during idle, which caused in an infinite tick()
loop (starts on first mouse move).

Now tick resets the animation on idle, and also, as a safety measure,
if we're past 1s after the animation deadline.

The safety measure is because the osc states are complex, and it's
easier to detect a "we really shouldn't be animating now" at tick()
itself rather than detecting the exact states where animation should
be reset. Generally, the safety mmeasure is not needed.

player/lua/osc.lua

@@ -2609,7 +2609,17 @@ function tick()
     state.tick_last_time = mp.get_time()
 
     if state.anitype ~= nil then
-        request_tick()
+        -- state.anistart can be nil - animation should now start, or it can
+        -- be a timestamp when it started. state.idle has no animation.
+        if not state.idle and
+           (not state.anistart or
+            mp.get_time() < 1 + state.anistart + user_opts.fadeduration/1000)
+        then
+            -- animating or starting, or still within 1s past the deadline
+            request_tick()
+        else
+            kill_animation()
+        end
     end
 end