Prevent clicking on disabled button

What does this MR do?

Fixes #29432 (closed)

Why was this MR needed?

While creating new project, if project title (AKA project path) is empty then GitLab export button is shown as disabled, but clicking on the same shows flash banner saying Please enter path and name for the project to be imported to, which is unnecessary since we're proactively keeping the button disabled when title is empty. This MR fixes two things around the flow.

• Clicking on GitLab export button, while it is disabled, does nothing.
• Project name input ignores white space as project name.

Screenshots

Before

After

Does this MR meet the acceptance criteria?

• Changelog entry added
• [ ] Documentation created/updated
• [ ] API support added
• Tests
  • [ ] Added for this feature/bug
  • All builds are passing
• Conform by the merge request performance guides
• Conform by the style guides
• Branch has no merge conflicts with master (if it does - rebase it please)
• Squashed related commits together

What are the relevant issue numbers?

Closes #29432 (closed)