Assumption:

If no message is selected, all menu selections that operate on selected
messages should be greyed-out/disabled.

Problem:

When no messages are selected, most (if not all) menu selections
that run operations on selected messages are still active.
These include:

File --> Open Selected Items
File --> Save As...
File --> Print...
Edit --> Delete
Edit --> Undelete
Edit --> Mark as Read
Edit --> Mark as Unread
Edit --> Mark All as Read
View --> Hide Selected Messages
Actions --> Reply
Actions --> Reply to All
Actions --> Forward 
Actions --> Forward As --> Quoted
Actions --> Forward As --> Attachment
Actions --> Forward As --> Inline
Actions --> Move to Folder
Actions --> Copy to Folder
Actions --> Apply Filters
Actions --> Expunge
Tools --> Create Filter From Message --> Filter On Subject
Tools --> Create Filter From Message --> Filter On Sender
Tools --> Create Filter From Message --> Filter On Recipients
Tools --> Create Virtual Folder From Message --> VFolder On Subject
Tools --> Create Virtual Folder From Message --> VFolder On Sender
Tools --> Create Virtual Folder From Message --> VFolder On Recipients

To reproduce the bug:

Select any empty folder and then test each of these menu selections.