Question - What are the features corrected by Autocad? 
          
        
        Answer - 
        Autocad detects the problem and correct it by removing the corruption with the drawing parts.  With the available option of adding additional vertices, it also adds vertices to the poly-lines. The error can be corrected or neglected by finding out the exact location of the poly-line that has zero vertices.  The object can be deleted or removed after there is no use of it in the system.