Bug#822755: Upstream known and fixed bug with qt 5.6

[Eric Valette]

So upstream beg to diffre and managed to reproduce the bug... Could you 
please rebuild with a fix...

https://quickgit.kde.org/?p=kcalc.git&a=commit&h=2678cb9c7a07381e3ffb8a2107946cec53bf5909