Update BinarySearch.java

[sanvi-05]

Input validation checks for a null input array, and if the input array is null, it throws an IllegalArgumentException with an error message indicating that the input array cannot be null. This ensures that the program handles invalid input cases where the input array is null.

Fixes #{ISSUE_NUMBER}

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[raj-j-shah]

@sanvi-05 Please refrain from sending pull requests directly. You must first be assigned to a task, after which your pull request will be reviewed and, if approved, merged.