Fix crash with older worker version requesting locustfile from master #4169

Job	Run time
Web UI Lint and Type Check	1m 38s
Build and Cache Packages	3m 32s
Test Docker Image	51s
Display metadata for build	3s
Ruff	58s
Mypy	1m 11s
Docs Build	59s
Linux	3m 51s
Windows	4m 44s
MacOS	3m 56s
Python 3.13	8m 55s
Python 3.12	8m 28s
Python 3.11	8m 28s
Python 3.10	8m 32s
Python 3.9	8m 39s
Publish prerelease on merge commit to master	0s
	1h 4m 45s

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