Fix incorrect handling of non-paginated repositories in fetchFirstCommitDate function

[haya08]

Description

This PR fixes a logic issue in fetchFirstCommitDate function where repositories without pagination (i.e., repositories whose commits fit within a single page) were not handled correctly.

Problem

In the previous implementation, when the Link header was absent (indicating no pagination), the function accessed the commit date but did not return it:
response.data[0].commit.author.date;

Solution

The updated implementation:

• Explicitly returns the commit date when pagination is not present.
• Stops execution early in the single-page case.
• Ensures empty repositories are handled properly.
• Preserves the original error message to improve debugging.

This guarantees correct behavior for:

• Empty repositories
• Single-page repositories
• Multi-page repositories

Impact

This change improves the reliability of first commit date extraction and prevents false failures when processing repositories without pagination.

[haya08]

@Relequestual can you please review this