Handle empty state for Projects.jsx after a ban removes mypage.html

[jhmullen]

Currently, if a student has no projects (initial default state), we autocreate mypage.html.

However, if enough of a student's content is banned such that they again "have no projects" (by way of a 0 length project list) then we attempt to recreate "mypage.html," which causes a collision in the unique naming of project files.

Handle this more gracefully.