fix(searches): handle empty list in jump_search

[Kanika0306]

Describe your change:

Fixes #15085

Added an early return guard if not arr: return -1 in jump_search() (searches/jump_search.py) to handle empty list inputs gracefully instead of raising an IndexError.

Also added a corresponding doctest, >>> jump_search([], 5), to verify that searching an empty list correctly returns -1.

• Add an algorithm?
• Fix a bug or typo in an existing algorithm?
• Add or change doctests? -- Note: Please avoid changing both code and tests in a single pull request.
• Documentation change?

Checklist:

• I have read CONTRIBUTING.md.
• This pull request is all of my own work -- I have not plagiarized.
• I know that pull requests will not be merged if they fail the automated tests.
• This PR only changes one algorithm file. To ease review, please open separate PRs for separate algorithms.
• All new Python files are placed inside an existing directory.
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[Kanika0306]

@mindaugl could you kindly review this pr
Thankyou