I can see. But the only problem I detect is in the definition of DIRECTIVES, no about the file size.
It seems to be a bug. I need to check it more.
By the moment, you can avoid the crash, including the definition of the attribute DIRECTIVE in the XML file:
<Attribute Name="DIRECTIVE" ForeCol="#a1a130"></Attribute>
And for a better highlighter, modify the definition for DIRECTIVES:
<Token Start="#" End="" Attribute='DIRECTIVE'> </Token>