Open Preview does not always open file in preview mode

[nimo23]

Bug Description:

Open Preview does not open the file in Preview mode if the file is not already open in Source mode.

Steps to Reproduce:

1. Go to Explorer and select any file that can be previewed (e.g. *.md file); this file should not already be opened in source mode (in another tab)
2. Right-click on this file from the Explorer and select the context menu item Open Preview.
3. Nothing happens. The file does not open.

If you open the file in "source mode" and then click Open Preview, the file will open successfully in "preview mode".

Additional Information

• Operating System:
• Theia Version: 1.55
• Mac OS