Bug 413363

SUMMARY


STEPS TO REPRODUCE
1. Start a clean desktop sessions (close all running applications)
2. Have "systemsettings5/Workspace/Startup and Shutdown/Desktop Session/On Login" set  to "Restore Previous session" and the list of "Applications to be excluded ..." containing anything but konqueror
3. Open a known (however arbitrary) number n of konqueror windows, e.g. showing $HOME and $TEMP
4. Log off and on again

OBSERVED RESULT
n Konqueror windows are correctly restored, plus one additional showing "about:blank"

EXPECTED RESULT
n instead of n+1 konqueror windows

SOFTWARE/OS VERSIONS
Windows: -
macOS: -
Linux/KDE Plasma: 4.15.0-67-generic #76-Ubuntu SMP
KDE Plasma Version:  5.17.1
KDE Frameworks Version: 5.63.0
Qt Version: Qt 5.13.1 (compiled against 5.13.1)

ADDITIONAL INFORMATION
The problem
1. seems to be some off-by-one error,
2. is not new, it has existed for many months (years?) and versions 
3. obviously has nothing to do with preloading. as it is independent of the settings in "Configure konqueror/Performance" (tested all 4 combinations)
4. does not reflect the setting "When konqueror starts:Show blank page", as you get an "about:blank" Windows even if "Show my start page" is configured

WORKAROUND
One can install wmctrl and set a login script that contains the line:
  bash -c 'sleep 5 ; wmctrl -c "about:blank — Konqueror" ' &
to silently close the gratituous window at each login.
(This is ugly, however, because each user has to do it individually.)