Channels can't find packages without packages_cache despite a previous 'fix'

[eugenesvk]

In this PR Mark the packages_cache as required you mention that the issue is fixed and:

I tested the forked channel and it functioned properly with the latest version of Package Control in the master branch.

However, after consistently failing to set up a custom channel, I realized that it's not really fixed and packages_cache is still required for the packages to be discovered. Neither the forked channel from the aforementioned PR, nor my simpler test with a single repository (of 4 packages) work properly with the latest ST/Package Control:

1st channel example, works: one repository with package_cache (only removed the dependencies cache)
2nd channel exmaple, fails: one repository without package_cache

1st debug log, works
2nd debug log, fails

Given that the logs are identical I realized it's not network-related and then after some digging found that the following changes to the caching mechanism in the fixCache branch of my fork that prevent the caching function from returning an empty data dictionary seem to fix the issue, though am not really certain what's going on, so a bit hesitant submitting a PR for this.

Would you please look into this packages_cache issue again?