Erasing grouped objects causes tdraw to display an error (2.6-beta-5)

[ffdixon]

Describe the bug
In 2.6.0-beta5, grouping two objects together and using the eraser causes a crash.

To Reproduce
Steps to reproduce the behavior:

1. Create two objects
2. Group them together
3. Erase them
4. An error dialog pops up on the viewer and sometimes the client

Expected behavior
A clear and concise description of what you expected to happen.

Actual behavior
A clear and concise description of what you expected to happen.

Screenshots

Reported in

https://groups.google.com/g/bigbluebutton-setup/c/U2XZFmyGBAI/m/rBZnSEZpBwAJ

See video from original post

error_crash.1.mp4

A snapshot of the error dialog when testing with the latest build

BBB version:

BigBlueButton Server 2.6.0-beta.5 (679)
                    Kernel version: 5.4.0-122-generic
                      Distribution: Ubuntu 20.04.5 LTS (64-bit)
                            Memory: 8148 MB
                         CPU cores: 4

[ffdixon]

Looks like there is an incoming fix! #16423

[ramonlsouza]

fixed by #16543