1004 - Empty string not allowed for property '%s'.
Description
    
A property was defined as a string with an empty value in a context where a non-empty string is required.
    
Example
    
Config:
    ObjectList( 'Obj' )
{
    .Compiler = '' // This should be a valid path
}
Output:
c:\Test\fbuild.bff(1):(1) FASTBuild Error #1004 - ObjectList() - Empty string not allowed for property '.Compiler'.
ObjectList( 'Obj' )
^
\--here
Fix:
ObjectList( 'Obj' )
{
    .Compiler = 'MyCompiler' // A previously defined Compiler()
}
