Fix gradient evaluation when one of coordinates is close to another #1776

Job	Run time
gcc-cmake-build (ubuntu-24.04-arm, gfortran-14, gcc-14, Debug)	3m 20s
gcc-cmake-build (ubuntu-latest, gfortran-14, gcc-14, Debug)	2m 28s
intel-meson-build (ubuntu-latest, ifort, icc)	7m 51s
gcc-meson-build (macos-latest, 14)	3m 48s
mingw-meson-build (MINGW64, x86_64)	5m 35s
gcc-meson-build (macos-latest, 13)	3m 21s
xtb-lightweight-meson-build (ubuntu-latest, gfortran-14, gcc-14)	1m 52s
gcc-cmake-build (ubuntu-24.04-arm, gfortran-14, gcc-14, Release)	4m 22s
gcc-cmake-build (ubuntu-latest, gfortran-14, gcc-14, Release)	3m 12s
gcc-meson-build (macos-latest, 12)	3m 49s
gcc-meson-build (ubuntu-latest, 14)	3m 51s
gcc-meson-build (ubuntu-latest, 12)	3m 57s
gcc-meson-build (ubuntu-24.04-arm, 14)	5m 30s
xtb-lightweight-cmake-build (ubuntu-latest, gfortran-14, gcc-14)	2m 27s
gcc-meson-build (ubuntu-22.04, 11)	3m 48s
gcc-meson-build (ubuntu-22.04, 10)	3m 54s
gcc-meson-build (ubuntu-latest, 13)	3m 37s
continuous-delivery	0s
	1h 6m 42s

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