#456 changing folders after decrypting

[Thomas Wabner]

After I have a encrypted message, for example in a IMAP
folder named "test" and decrypt it:

Switching between the "test" folder to, for example
INBOX, the INBOX folder show message from the test folder.

It looks like, that the creation of a temporary message
for the decrypted message is not refreshed (or deleted)
after switching the folders.

Have a look into the PGPMessageFilter#decrypt

line "return filter(folder, uid, message);"

I don't understand exactly what we do here.