Potential bug/leak: middleware cache grows even if no middleware created

[BrainCrumbz]

Description

TL;DR: when videojs players are instantiated and disposed repeatedly on page, middlewareInstances keeps growing with new keys and null values.

We are hunting potential memory leaks in our video-based app. Comparing heap snapshots on Windows Chrome and Android Chrome, we noticed a (small?) amount of property arrays due to middlewareInstances. Snapshot were taken after disposing a player once, and then after instantiating/disposing e.g. 10 times.

Adding logpoints in tech/middleware.js, we noticed that:

1. getOrCreateFactory is never called, so no new entry is set in middlewareInstances for a new player
2. clearCacheForPlayer is called every time player is disposed, so a new, null-valued entry is added to middlewareInstances

This happens for videojs v7.20.3. Comparing file with latest revision showed no significant change, so maybe the behaviour is the same in latest code.

If everything is correct, would you consider a tiny PR that addresses this? E.g. clearCacheForPlayer could check if key exists in the first place?

Thanks

Reduced test case

None. Willing to create one if issue is of interest

Steps to reproduce

1. After page load, create a player with videoPlayer = videojs(videoElem, videoPlayerOptions); and set a source on it with videoPlayer.src({src: ..., type: ...})
2. After a timeout, dispose player with videoPlayer.dispose();
3. After a timeout, repeat the process e.g. twice

Errors

None

What version of Video.js are you using?

7.20.3

Video.js plugins used.

None

What browser(s) including version(s) does this occur with?

Chrome 123

What OS(es) and version(s) does this occur with?

Windows 11

[mister-ben]

A PR would be welcome, thanks.

[BrainCrumbz]

PR can be found at #8674

Waiting for comments etc. Bye!