Lock out kmail when trying to delete text in a 25000 line email

 Hi

I've got  problem that i cannot seem to escape from.  I replied to the opensuse Tumbleweed automated snapshot email for 201709013 and tried to "snip" out most of it by pressing Ctrl "a" to highlight all the text in one go so i could then just press [Delete]  to remove them all.  
The problem is that its now gone into some sort of vacuum with the kmail main window and the reply window open but i'm unable to do anything.  Its running at 50% cpu. 
I cannot kill the reply composer window without killing the main window.  If i do kill the windows and reload kmail both windows open again but i only get the window title bar and the borders of the window.  

How can you kill a reply composer window with out killing kmail? 

Kmail finally finished (about 30 minutes later)  whatever it was doing and i finally got the focus back

I've cross posted this to opensuse-factory as well

 regards

 Ian

-- 
opensuse:tumbleweed:20170913
Qt: 5.9.1
KDE Frameworks: 5.37.0
KDE Plasma: 5.10.5
kwin 5.10.5
kmail2 5.6.1
akonadiserver 5.6.1
Kernel:  4.13.1-1-default
Nouveau:  1.0.15_1.2