Fix use of ST_MSGN as sequence method

[gioid]

When we upgraded from version 2.7.2 to 4.1.0 of this library we noticed bugs and sneaky behaviours using the sequence method ST_MSGN.
We think that these two issues suffered the same behaviours that we noticed:

• MessageCollection has "total" > 0 but "items" is empty? #341
• Can't retrieve messages, always returns 0 laravel-imap#454

We checked the differences among old version and new version. We found that the main issue regards the use of the $uid variable in the "fetch" method of the ImapProtocol class. The old version used that variable as a boolean while the new code treats it sometimes as bool and sometimes as int|string.

This pull request restored the old behaviour and with these changes we can see our code started work again.
Can you please check it and understand if you want to merged it in the master branch?

[didi1357]

+1

Did not run into the bug, but saw it in code when looking for how to ensure that UIDs are used. Fortunately for me, they are default in this library in a lot of places and PHP seems to treat the newly introduced constant IMAP::ST_UID as true in many places. However, the current code for sure will not work properly with the message numbers constant.

@gioid seems to have found all occurences of the problem and fixed the comparisons. I approve and would merge his changes. However, I have no write access. Just my two cents as info for @Webklex. :)

[Webklex]

Hi @gioid ,
many thanks for your pull request as well as time and effort to look for all occurrences.

Best regards,