Fix issue with bedrock_autoloader option

[slackday]

This fixes an issue where the bedrock_autoloader option is set but the number of plugins differs. I ran into this issue when moving a plugin from plugin to mu-plugin and deploying to a remote server.

I haven't been able to recreate this in a reliable way but having ran into this issue a couple of times on different servers I figured I'd propose my fix.

Basically $cache will not evaluate to false because it will be set to an array looking like this:

array(
'plugins' => array(),
'count' => 0,
);

This fixed it for me.

I created the issue in the wrong project. And instead of spamming new issue here you can read my original issue on the Trellis-project roots/trellis#1022.

If you want me to open issue here anyway I can do it.

[swalkinshaw]

This seems to make sense. We'll have to try it out first.