Fix: Axes.bar StopIteration on all-NaN x (regression) — swev-id: matplotlib__matplotlib-24149

[casey-brooks]

Summary

• fall back to safe_first_element when _safe_first_finite raises StopIteration in Axes._convert_dx
• add regression coverage for NaN-only bar inputs

Testing

Resolves #34

[casey-brooks]

Test & Lint Summary

• PYTEST_ADDOPTS='-W default::DeprecationWarning' MPLBACKEND=Agg LD_LIBRARY_PATH=/root/.nix-profile/lib:/nix/store/qipd93x9gjyiygqk673rd2ssnf8y7jj0-gcc-14.3.0-lib/lib:/nix/store/f8w1i7yisixb9hivzbk0l4ixmf67fjqr-gcc-14.3.0-libgcc/lib: .venv/bin/pytest -q lib/matplotlib/tests/test_axes.py::test_bar_all_nan_x_and_height_no_stopiteration (passed, 1 warning)
• PYTEST_ADDOPTS='-W default::DeprecationWarning' MPLBACKEND=Agg LD_LIBRARY_PATH=/root/.nix-profile/lib:/nix/store/qipd93x9gjyiygqk673rd2ssnf8y7jj0-gcc-14.3.0-lib/lib:/nix/store/f8w1i7yisixb9hivzbk0l4ixmf67fjqr-gcc-14.3.0-libgcc/lib: .venv/bin/pytest -q lib/matplotlib/tests/test_axes.py::test_bar_nan_x_zero_height_no_stopiteration (passed, 1 warning)
• PYTEST_ADDOPTS='-W default::DeprecationWarning' MPLBACKEND=Agg LD_LIBRARY_PATH=/root/.nix-profile/lib:/nix/store/qipd93x9gjyiygqk673rd2ssnf8y7jj0-gcc-14.3.0-lib/lib:/nix/store/f8w1i7yisixb9hivzbk0l4ixmf67fjqr-gcc-14.3.0-libgcc/lib: .venv/bin/pytest -q lib/matplotlib/tests/test_axes.py::test_bar_zero_x_nan_height_baseline_ok (passed, 1 warning)
• .venv/bin/flake8 lib/matplotlib/axes/_axes.py (passed)
• .venv/bin/flake8 lib/matplotlib/tests/test_axes.py --extend-ignore=E721 (passed)

[noa-lucent]

Looks good to me.