Single page scan: If reading the scanner resolution raises an error, use the one defined in the configuration.
(It seems some scanner accept changing this setting, but not reading it)

Signed-off-by: Jerome Flesch <jflesch@gmail.com>
Main window: fix warning message formating

Signed-off-by: Jerome Flesch <jflesch@gmail.com>
Merge branch 'testing' into wip-progressive-doclist-display