Avoid incorrect filtering on the list in persp-read-persp when loading persps from file.

[roife]

Fix #145 .

This bug arises when a persp-list is passed to persp-read-persp, causing the function to execute incorrect filtering operations on the list. These filtering operations rely on the assumption that the list contains perspectives that are active. However, when using persp-load-from-file-by-names, the perspectives within the list haven't been loaded, which leads to error.

[roife]

I'm wondering if it is an elegant solution. Comments or suggestions are welcome.