Diagrams with more than 1 page get corrupted

[DataPlusProgram]

Using plugin version 1.5.0 on Windows any diagram with more than 1 page will get corrupted for me.

Steps to reproduce:

• View a diagram with 2 pages
• Switch to the second page you will get an error saying "Cannot set property 'innerHtml' of null"
• Switch to any other document
• Switch back to the diagram and all but the first pages will have been deleted.
• The plugin will save the corrupted diagram to disk erasing the pages permanently.

[RyanQuey]

I ran into this as well, if it weren't for good backups I'd be in a world of hurt :)