Fix TypeError with empty axes in FFT functions #729

Job	Run time
build_linux (3.10, 2.2)	3m 27s
build_windows (3.14, 2.3)	13m 47s
build_windows (3.11, 2.3)	7m 56s
build_linux (3.13, 2.3)	3m 21s
build_windows (3.10, 2.2)	7m 53s
build_windows (3.13, 2.3)	8m 17s
build_windows (3.12, 2.3)	9m 5s
build_linux (3.14, 2.3)	3m 25s
build_linux (3.11, 2.3)	4m 13s
build_linux (3.12, 2.3)	3m 40s
test_linux (3.14, numpy">=2", false, ubuntu-latest)	2m 1s
test_linux (3.11, numpy">=2", false, ubuntu-latest)	1m 50s
test_linux (3.10, numpy">=2", false, ubuntu-latest)	1m 45s
test_linux (3.12, numpy">=2", false, ubuntu-latest)	1m 35s
test_linux (3.13, numpy">=2", false, ubuntu-latest)	1m 32s
test_windows (3.13, numpy">=2", false, windows-latest)	3m 28s
test_windows (3.11, numpy">=2", false, windows-latest)	3m 22s
test_windows (3.12, numpy">=2", false, windows-latest)	3m 42s
test_windows (3.14, numpy">=2", false, windows-latest)	3m 17s
test_windows (3.10, numpy">=2", false, windows-latest)	3m 39s
	1h 31m 15s

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