Fix row creation in empty child table & add min-width to childtable ui

[Siddhantsingh1230]

Description

This PR fixes row creation in the Project Detail page when the child table is initially empty.
The issue was caused by using rows[rows.length - 1].idx + 1, which fails when rows is an empty array, as rows[-1] is undefined. This PR also adds a minimum width to the child table to ensure better accessibility and usability on smaller screens.

Relevant Technical Choices

• Calculate newIdx based on array length, if length is zero assign 1 to the new row

Testing Instructions

• Go to NPMS
• Open Project Page
• Open any Project
• Add row to empty child table

Additional Information:

None

Screenshot/Screencast

Before:

Add.Row-1753272231002.mp4

After:

Fix.Child.table.-1753272061638.mp4

Checklist

• I have carefully reviewed the code before submitting it for review.
• This code is adequately covered by unit tests to validate its functionality.
• I have conducted thorough testing to ensure it functions as intended.
• A member of the QA team has reviewed and tested this PR (To be checked by QA or code reviewer)