If a folder is empty, most servers will return EXISTS 0 and imaplib2
passes back ['0'] as return value to a select(). It returns [None] if
no EXISTS response was given by the server at all.
Attempting to fetch the UIDs of 0 emails which leads to
various error messages (One server responds with "NO No matching
messages", Gmail seems to say "BAD Bad message sequence 1:*" for some
(although it is working fine for me with Gmail, so it might behave
different for different people).
In case we get an None or 0 back, we simply stop caching messages as the
folder is empty. This should fix the various error reports that have
popped up.
Signed-off-by: Sebastian Spaeth <Sebastian@SSpaeth.de>
Signed-off-by: Nicolas Sebrecht <nicolas.s-dev@laposte.net>
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