Double clicking PDF attachment in "sections" tab does not open file in default program and gives error instead.

[RickKukiela]

Describe the bug
I sent myself a test email that contains a PDF file attachment. To verify the email worked I wanted to open the attachment. I double clicked on the section for the file and was shown this error widow:

I was able to right click the section for the file, and choose save as, where I was able to save a copy to my desktop. The file it saved to the desktop did open correctly in my Adobe Acrobat software.

There is a default application configured for this file type in my system so I don't think it's related to that.

I tried again using an attachment without spaces in the filename and the same issue occurred.

I think the application is trying to run the PDF file like its an executable rather than trying to run the application for which the file is for, though I cannot offer any thoughts as to why or how to resolve it.

I don't mind having to save as to work around this for now, but I just wanted to let you know.

I am using version 7.0.0