Double-click on textbox causes NullReferenceException

after many undos followed by double click on text box that somehow had it text cleared, not sure how clearing of text box was triggerered

Software version: 1.2.9.112-RELEASE-9bc62ac42bd37d7ba2b19946b70d40a599332b75 (64 bit)
.NET runtime version: 4.0.30319.42000+
Time: 2017-01-10 10:14:25 +01:00
OS: unknown (x64) 6.1 build 7601 revision 10000
GDI object count: 199
User object count: 98

Exception: System.NullReferenceException
Message: Object reference not set to an instance of an object.

Stack:
at Greenshot.Drawing.TextContainer.EnsureTextBoxContrast()
at Greenshot.Drawing.TextContainer.ShowTextBox()
at Greenshot.Drawing.DrawableContainerList.OnDoubleClick()
at Greenshot.Drawing.Surface.SurfaceDoubleClick(Object sender, MouseEventArgs e)
at System.Windows.Forms.Control.OnMouseDoubleClick(MouseEventArgs e)
at System.Windows.Forms.Control.WmMouseUp(Message& m, MouseButtons button, Int32 clicks)
at System.Windows.Forms.Control.WndProc(Message& m)
at System.Windows.Forms.NativeWindow.Callback(IntPtr hWnd, Int32 msg, IntPtr wparam, IntPtr lparam)

Configuration dump: