Fix index out of range exception (#35031)

[sheerluck]

📚 Description

We return False if there is no n-th path

Closes #35031

📝 Checklist

• I have made sure that the title is self-explanatory and the description concisely explains the PR.
• I have linked an issue or discussion.
• I have created tests covering the changes.
• I have updated the documentation accordingly.

[codecov-commenter]

Codecov Report

Base: 88.57% // Head: 88.59% // Increases project coverage by +0.01% 🎉

Coverage data is based on head (d9f9a36) compared to base (52a81cb).
Patch coverage: 100.00% of modified lines in pull request are covered.

Additional details and impacted files

@@             Coverage Diff             @@
##           develop   #35156      +/-   ##
===========================================
+ Coverage    88.57%   88.59%   +0.01%     
===========================================
  Files         2140     2140              
  Lines       397273   397276       +3     
===========================================
+ Hits        351891   351963      +72     
+ Misses       45382    45313      -69     

Impacted Files	Coverage Δ
src/sage/plot/arrow.py	94.33% <100.00%> (+0.10%)	⬆️
src/sage/modular/local_comp/liftings.py	98.33% <0.00%> (-1.67%)	⬇️
src/sage/cpython/_py2_random.py	75.20% <0.00%> (-1.24%)	⬇️
src/sage/graphs/generators/random.py	91.43% <0.00%> (-1.03%)	⬇️
src/sage/groups/generic.py	88.34% <0.00%> (-0.68%)	⬇️
...sage/geometry/hyperbolic_space/hyperbolic_model.py	88.95% <0.00%> (-0.62%)	⬇️
src/sage/categories/weyl_groups.py	96.47% <0.00%> (-0.59%)	⬇️
src/sage/doctest/reporting.py	74.45% <0.00%> (-0.44%)	⬇️
src/sage/modular/overconvergent/hecke_series.py	98.76% <0.00%> (-0.31%)	⬇️
src/sage/combinat/posets/lattices.py	92.26% <0.00%> (-0.10%)	⬇️
... and 20 more

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[videlec]

Thanks for the bug fix. You must add a doctest that shows that the error is indeed corrected. Ideally this would go inside a TESTS block such as this example taken from complex_mpfr.pyx

         Check that :trac:`14989` is fixed::

            sage: QQi = NumberField(x^2+1, 'i', embedding=CC(0,1))
            sage: i = QQi.order(QQi.gen()).gen(1)
            sage: CC(i)
            1.00000000000000*I

See https://doc.sagemath.org/html/en/developer/coding_basics.html for the formatting of docstrings.

[videlec]

Your example already "works" fine on sage 9.5 (in the sense that it does return Launched png viewer for Graphics object consisting of 1 graphics primitive). On which sage version is it supposed to fail?

[videlec]

Do you mean to use arrow((0,0), (0,0), linestyle='dashed') as in the issue?

[sheerluck]

Do you mean to use arrow((0,0), (0,0), linestyle='dashed') as in the issue?

I made a mistake but then force pushed correct version

[videlec]

Do you mean to use arrow((0,0), (0,0), linestyle='dashed') as in the issue?

I made a mistake but then force pushed correct version

Looks better now :)

[videlec]

Just waiting for the CI before giving a positive review.

[github-actions]

Documentation preview for this PR is ready! 🎉
Built with commit: d9f9a36

[seblabbe]

I see that the Build & Test is failing, but the error:

----------------------------------------------------------------------
sage -t --random-seed=225549214259244020593978072013798380016 doc/ca/intro/index.rst  # 1 doctest failed
----------------------------------------------------------------------

is not related to this ticket.

[seblabbe]

Changes look good to me.