Fix bug where preview sometimes wasn't shown for cubic panoramas.
Fix bug where preview sometimes wasn't shown for cubic panoramas.

mpetroff/pannellum,Benvii/pannellum,quentinyang/pannellum,mpetroff/pannellum,Benvii/pannellum,psteph801/psteph801.github.io,Benvii/pannellum,ywjrg/pannellum,psteph801/psteph801.github.io,eric-seekas/pannellum,ywjrg/pannellum,quentinyang/pannellum,riuson/pannellum,eric-seekas/pannellum,quentinyang/pannellum,riuson/pannellum,Benvii/pannellum,riuson/pannellum,eric-seekas/pannellum,ywjrg/pannellum,mpetroff/pannellum,quentinyang/pannellum,mpetroff/pannellum,psteph801/psteph801.github.io,psteph801/psteph801.github.io,ywjrg/pannellum,riuson/pannellum,eric-seekas/pannellum