Fix caching takes place in multi-site if plugin is activated on one s…

[8ctopus]

Fix caching takes place in multi-site if plugin is activated on one site and disabled on another one that is a subfolder of the first one

Proposed fix for #343

[futtta]

I can confirm this clean & simple change works on my local multisite install. Maybe add an is_multisite() check in there as extra condition?

[8ctopus]

@futtta Thank you for testing it. What would is_multisite() bring?

[futtta]

It would make sure to limit the behavior to multisite, where the actual problem occurs?

[8ctopus]

@futtta correct me if I'm wrong, my understanding is that this code is only executed on single-site if the plugin is enabled, therefore not strictly necessary.

[8ctopus]

I had to move the code because otherwise the page was never delivered from cache if Apache was not delivering the cache.