Calling while on DND mode causes a viewer crash (Alchemy 6.3.4 Test Build)

Summary

Lately I have encountered an issue where the viewer crashes when another individual starts a call while I am on DND mode, and instead of automatically declining it, the viewer freezes and will stay that way until I end the process by clicking on the x button a few times to close it out.

Steps to reproduce

Simply switching to Do Not Disturb mode and having someone try calling you ends up crashing the viewer.

What is the current bug behavior?

The viewer crashes after this is done.

What is the expected correct behavior?

The viewer should automatically decline it without crashing when another individual calls while the user is on DND mode.

Environment

(Please open Help->About Alchemy and use Copy to Clipboard then paste its contents within the code blocks below)

Alchemy 6.3.4 (132) (64 bit) Dec 12 2019 19:30:48 (Alchemy Project FluffyFox) (B)
Release Notes

You are at 129.2, 126.8, 1000.1 in Serenity Garden located at sim10111.agni.lindenlab.com (216.82.48.177:13008)
SLURL: http://maps.secondlife.com/secondlife/Serenity%20Garden/129/127/1000
(global coordinates 194177.0, 343423.0, 1000.1)
Second Life Server 2019-12-04T20:29:26.533447
Release Notes

CPU: Intel(R) Core(TM) i7-7700HQ CPU @ 2.80GHz (2808 MHz)
Memory: 16304 MB
OS Version: Microsoft Windows 10 64-bit (Build 18363)
Graphics Card Vendor: NVIDIA Corporation
Graphics Card: GeForce GTX 1050 Ti/PCIe/SSE2

Windows Graphics Driver Version: 26.21.14.4166
OpenGL Version: 4.6.0 NVIDIA 441.66

Window size: 1920x986
Font Size Adjustment: 96pt
UI Scaling: 1
Draw distance: 512m
Bandwidth: 3000kbit/s
LOD factor: 4
Render quality: 0
Advanced Lighting Model: Enabled
Texture memory: 1904MB
VFS (cache) creation time: December 16 2019 17:30:22

RestrainedLove API: (disabled)
libcurl Version: libcurl/7.66.0 OpenSSL/1.1.1d zlib/1.2.11 WinIDN nghttp2/1.39.2
J2C Decoder Version: OpenJPEG: 1.5.1, Runtime: 1.5.1
Audio Driver Version: FMOD Studio 2.00.03
Font Decoder Version: FreeType 2.10.1
Dullahan: 1.3.201911222103 / CEF: 78.3.7+gea7ef34+chromium-78.0.3904.108 / Chromium: 78.0.3904.108
LibVLC Version: 2.2.8
Voice Server Version: Vivox 4.10.0000.32327

Built with MSVC version 192428314
Packets Lost: 0/3716 (0.0%)
December 16 2019 20:08:55

Relevant logs and/or screenshots

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