Steps to reproduce:

1. Have some process discovery and item prototypes for monitoring memory usage
2. Have a macro {$PROC_MAX_MEMORY:someProcessName} with value '1G'
3. Have some trigger(prototype) using an expression containing the context-macro ie. '{discovered item} > {$PROC_MAX_MEMORY:"{#PROCNAME}"}'
4. Change the amount of allowed memoryUsage and make some typo by changing the value to '1GG'

I didn't test these exact steps, but I came across this problem. suddenly zabbix_server crashed and after restart it immediately crashes again. After thinking and double-checking the changes I made, and the 'DCexpression_expand_user_macros' in the backtrace, I noticed this typo. Removing the double 'G' fixed the issue, the server started again without issues.

Result:
zabbix_server crashes
See backtrace (attachment)

Expected:
Some 'Not Supported' state with some indication there is an issue with a trigger expression