Properly unset proxy env if empty #28

Job	Run time
Upload debug artifacts after failure in analyze (default)	1m 30s
Upload debug artifacts after failure in analyze (linked)	1m 32s
Upload debug artifacts after failure in analyze (stable-v2.20.3)	1m 32s
Upload debug artifacts after failure in analyze (nightly-latest)	1m 36s
Download and check debug artifacts after failure in analyze	5s
	6m 15s

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