1011 - Unnamed modification must follow a variable assignment in the same scope.
Description
    
A variable modification operator was used without specifying the variable to append to. This is supported, provided the
destination variable was previously referenced.
    
Example
    
Config:
           + 'String' // BAD - No variable to assign to
Output:
c:\Test\fbuild.bff(1):(7) FASTBuild Error #1011 - Unnamed modification must follow a variable
assignment in the same scope.
      + 'String'
      ^
      \--here
Fix:
.MyVar = 'hello'
       + 'String' // OK - The destination variable can be inferred
    