Can not expand/collapse if PDF is in landscape.

[thammawat-s]

When PDF file size is a landscape (width is larger than height), it won't expand after collapsing couple times. Same behaviour on both mobile and desktop. I attach some sample PDFs. Thanks again for this plugin. Best regards,

To reproduce:

1. add the pdf file
2. click collapse, wait a bit
3. click expand
4. click collapse, wait a bit
5. click expand <-- this will not expand

flyer_a6_mass.pdf
A5 Diary.pdf
blank.pdf