1400 - 'Dest' with multiple 'Source' files should be a path. Missing trailing '/'?

Description
A Copy() target was declared with multiple .Source files, but .Dest was not a path. If the .Dest is a file, then only one .Source can be specified. If .Dest is intended to be a path, it requires a trailing slash to disambiguate.
Example
Config:
Copy( 'MissingTrailingSlash' ) { .Source = { 'Files/a.txt' 'Files/b.txt' } .Dest = 'Folder/Folder' // NOTE: Missing trailing slash }
Output:
c:\test\fbuild.bff.bff(1,1): FASTBuild Error #1400 - Copy() - 'Dest' with multiple 'Source' files should be a path. Missing trailing '/'? Copy( 'MissingTrailingSlash' ) ^ \--here
Fix:
Copy( 'Good' ) { .Source = { 'Files/a.txt' 'Files/b.txt' } .Dest = 'Folder/Folder/' // NOTE: Trailing slash }