gpujpegtool: avoid some error on unknown extension #206

Job	Run time
retag-continuous	3s
run Ubuntu (all)	8m 32s
run Ubuntu (legacy)	4m 14s
run Windows (legacy, GPUJPEG-Windows, 35, https://developer.download.nvidia.com/compute/cuda/11.8...	7m 38s
run Windows (all, GPUJPEG-Windows-all, all, https://developer.download.nvidia.com/compute/cuda/12...	14m 11s
	34m 38s

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