Application crash from unhandled exception when image load fails

[adron1111]

Issue description

MarkdownViewerPlusPlus makes Notepad++ crash when an attempt to load an image fails. In this case, the HTTPS connection cannot be established.

Markdown to reproduce

## Allmänt

Allmänt 49357  

-   Bilaga ![Mastery Connect](https://hkr.instructure.com/images/icons/mc-assignment-pub.svg) 
  

Screenshot

Environment

• Notepad++ 8.7 (x86)
• MarkdownViewer++ 0.8.2.25525
• Windows 10 (x64)