**System Information**
Operating system: macOS-10.14.6-x86_64-i386-64bit 64 Bits
Graphics card: Intel(R) Iris(TM) Plus Graphics 655 Intel Inc. 4.1 INTEL-12.10.25
**Blender Version**
Broken: version: 3.0.0 Alpha, branch: master, commit date: 2021-08-16 16:57, hash: `rB4dba2060118b`
2.93.2, branch: master, commit date: 2021-08-03 05:58, hash: `rB1eb06de2607a`
**Short description of error**
I have two bones A and B, A has a custom property name 'a', B has none, in pose mode, select B and shift select A, press alt+LMB click and slide to change the custom property 'a', crash happens every time. If B has a custom property but with a different name, crash happens as well
I know this operation doesn't make sense, you can't change a property that doesn't exist on some of the selected objects, but sometimes irrelevant bones are selected unintentionally, and crashes are annoying, if properties don't exist just do nothing
**Exact steps for others to reproduce the error**
1.create two bones in one armature object, name them A, B
2.switch to pose mode
3.select A, in the Bone properties panel add a custom property name 'a'
4.select B, shift select A, go to Bone properties panel find custom property 'a', press alt and LMB click and slide on the value of custom property 'a', crash happens
{F10286229}