Fix canvas crop

[DimK10]

Description

Fixes the bug

Closes #(issue_number)

Checklist

• [x] I have read the Contribution Guidelines
• [x] I have performed a self-review of my own code
• [] I have attached images of the change if it is UI based
• [x] I have commented my code, particularly in hard-to-understand areas
• [x] My changes generate no new warnings
• [] I have read the section Add New Translation Tags (for new translation tags only)

[DimK10]

Haven't tested with a pdf that has multiple pages. Should work though.