Bug: Crash when click-drag corner of rectangle to enlarge

Librecad 2.2.0-alpha (as displayed in the LibreCAD "help" menu), but listed as 2.1.1+20161015.416.0~ubuntu16.04.1 in Synaptic package manager

Operating System LinuxMint18, Mate desktop

Installed from PPA deb http://ppa.launchpad.net/librecad-dev/librecad-daily/ubuntu xenial main

Draw polyline rectangle.  Click resulting rectangle to select it.  Click-drag corner of rectangle to new location to enlarge it.  Click to set this new point.  LibreCAD crashes, with the following message in dmesg:

[774189.082863] librecad[22928]: segfault at 10 ip 000000000058f4d4 sp 00007fff3deed820 error 4 in librecad[400000+70c000]

100% repeatable, using several different LibreCAD drawings to test with.

Update:

After more testing, this bug only seems to happen for EXISTING polylines in all of my drawings that have been saved, and then the file reopened.  If I add a NEW polyline to one of the drawings that is currently experiencing problems, things work for that NEW polyline.  But not for any of the existing ones.  This is weird.  Especially because all the drawings that are having problems were created using the same version of LibreCAD as I was using during this testing.  On the same computer too.

2nd update:

I found that if I open a drawing and immediately try the click-drag as reported, LibreCAD crashes.  However, if I FIRST add a new element - a random 2-point line is good enough - then I can go back and click-drag a corner of the old element that was giving me problems just fine.  LibreCAD does not crash any more.  If I save the drawing that is now working, then reopen it, LibreCAD crashes again if I try the click-drag.

So the workaround seems to be: Open drawing, immediately add random new element, delete random new element, then go about your regular business.  Do this every time you open an existing LibreCAD drawing.

I'm unable to reproduce this on OS X with Qt 5.6.1.

I am able to reproduce it on openSUSE and Qt 5.6.1...
I wonder if it's a difference between clang and gcc...

https://github.com/LibreCAD/LibreCAD/issues/830