Fixes error raised when using multiple files for fields with no time dimension #618

Job	Run time
py3.13 \| macos \| integration tests	16m 47s
py3.13 \| macos \| unit tests	12m 50s
py3.13 \| ubuntu \| integration tests	17m 32s
py3.13 \| ubuntu \| unit tests	13m 31s
mypy	3m 38s
py3.13 \| windows \| integration tests	31m 32s
py3.13 \| windows \| unit tests	21m 53s
py3.10 \| ubuntu \| unit tests	13m 13s
py3.10 \| ubuntu \| integration tests	25m 31s
py3.11 \| ubuntu \| unit tests	13m 45s
py3.12 \| ubuntu \| unit tests	14m 5s
merge-test-artifacts	2s
	3h 4m 19s

Provide feedback