Fix TypeError with empty axes in FFT functions #895

Job	Run time
build_windows (3.13)	7m 44s
build_windows (3.14)	8m 14s
build_windows (3.12)	8m 55s
build_windows (3.11)	8m 8s
build_linux (3.14)	3m 33s
build_linux (3.11)	3m 22s
build_linux (3.10)	3m 29s
build_linux (3.13)	3m 27s
build_linux (3.12)	3m 38s
build_windows (3.10)	12m 59s
test_linux (3.13, false, ubuntu-latest)	1m 46s
test_linux (3.10, false, ubuntu-latest)	1m 52s
test_linux (3.11, false, ubuntu-latest)	2m 4s
test_linux (3.14, false, ubuntu-latest)	1m 51s
test_linux (3.12, false, ubuntu-latest)	1m 38s
test_windows (3.12, false, windows-latest)	3m 52s
test_windows (3.13, false, windows-latest)	3m 29s
test_windows (3.10, false, windows-latest)	3m 45s
test_windows (3.14, false, windows-latest)	3m 11s
test_windows (3.11, false, windows-latest)	3m 31s
	1h 30m 28s

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