Team Library folders show modified date of 1970

### Current Behavior

When viewing the team library, folders are showing a modified date of Jan 1, 1970.

### Expected Behavior

Either be blank, or show the most recent modified date of the contents. Propose the former as the quick fix.

### Steps To Reproduce

_No response_

### Environment

- FlowFuse version:
- Node.js version:
- npm version:
- Platform/OS:
- Browser:

### Have you provided an initial effort estimate for this issue?

I have provided an initial effort estimate