Solution for Kmail crash in libKF5MessageViewer.so.5 with 'No Header Style plugin found'

[Vasily Galkin]

I'm not filing a bug since I unfortunately doesn't know exact steps that lead to the situation:
The steps was something like
-I used KMail for 4 years with a lot of reconfiguration every 1-2 years under non-KDE desktop.
-copied some of my .dot dirs from debian 7-8 $HOME to fresh installed debian 10 $HOME
-tried to disable some random seemingly unused by me akonadi services via akonadiconsole (understand that it is a bad idea, maybe this was the main problem reason)

The result was: KMail crashing in libKF5MessageViewer.so.5 in ViewerPrivate::renderAttachments while displaying most of the messages, I think those that had any attachments and outputs in the terminal:
org.kde.pim.messageviewer: No Header Style plugin found

And other problems similar to https://bugzilla.redhat.com/show_bug.cgi?id=1516488 (but kdepim-addons was already installed).

Posting the solution for my case here just in case it comes in handy for somebody:
- found that my ~/.config/pimpluginsrc file under [HeaderStylePlugins] section had all plugins in "PluginHeaderStyleDisabled" list with empty PluginHeaderStyleEnabled list
- After editing config - moving all plugins from Disabled list to Enabled list - kmail works fine.

BTW, huge thanks to KMail developers!
While there is some minor problems in "very corner" cases like I mentioned above, for the last 4-5 years KMail is pretty stable and intuitive!

--
Vasily