[Bug] MindForger will not open markdown files that do not contain headings

[fyodorovich]

Bug description:
MindForger will not open markdown files that do not contain headings.
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Expected behaviour:
Mindforger should be able to open and display markdown files. Markdown does not specify that a heading must be in the file. Any other text editor will open these files. Any markdown viewer or editor will open these files.
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Environment:

• MindForger version: MindForger 1.54.0
• Operating system: 13.6 (22G120)

Steps to reproduce 🐞:

1. Use the menus or the icons to open a markdown file
2. Select a file which does not contain headings
3. The notebooks list is displayed - empty - and the file is not opened