Resolve issue #12679

[Yokyeee1114]

Fixes TEAMMATES#12679
Outline of Solution
My teammates and I analyzed and discussed the ts file for detecting the input of newfeedbacksessionname.
We found that the field was not checked for validity before the copy button was pressed.
We have now added a series of methods such as trim() to determine whether there are illegal spaces in the field.

Outline of Solution

[github-actions]

Hi @Yokyeee1114, thank you for your interest in contributing to TEAMMATES!
However, your PR does not appear to follow our contribution guidelines:

• Title must start with the issue number the PR is fixing in square brackets, e.g. [#<issue-number>]
• Description must reference the issue number the PR is fixing, e.g. Fixes #<issue-number> (or Part of #<issue-number> if the PR does not address the issue fully)

Please address the above before we proceed to review your PR.

[u7721487]

Solved #1 Code is easy to read and work well in my environment

[Yokyeee1114]

I already fixed it but for somehow the test didn't pass.