The only reason our code wants PKCS12 files is for a private key, but
a valid file needn't contain one; and reading a file without lead to a
crash in QSslKeyPrivate::fromEVP_PKEY(). So check for missing key and
fail the load, since the file is useless to us. Also ensure the
caller's pkey is initialized, as we aren't promised that
PKCS12_parse() will set it when there is no private key.
Add a test for this case (it crashes without the fix) and update the
instructions for how to generate test data to cover it also.
(Corrected the wording there, too; at the interactive prompt,
"providing no password" really provides an empty password.)
Task-number: QTBUG-62335
Change-Id: I617508b903f6d9dee40d539b7136b0be8bc2c747
Reviewed-by: Timur Pocheptsov <timur.pocheptsov@qt.io>
b9557296cb