mod_storage_xep0227: treat roster metadata pseudo-entry correctly
The roster version is stored in a pseudo-item which has the key `false`.
The if condition in the touched code attempts to guard against this, but
it does not take into account that the jid prepping returns nil instead
of false.
By moving the jid prepping into the if, we can check for the metadata
entry safely.
Thanks for your interest in contributing to the project!
There are many ways to contribute, such as helping improve the
documentation, reporting bugs, spreading the word or testing the latest
development version.
You can find more information on how to contribute at <https://prosody.im/doc/contributing>
See also the HACKERS and README files.