NPE occurs when generating dot file of an NFA #769
Description
I chose exactly the lexer in examples/simple and appended "-dot" argument. Then the following NPE occurred:
../../bin/jflex -d out/genfiles -dot src/main/jflex/simple.flex
Reading "src/main/jflex/simple.flex"
Constructing NFA :
Unexpected exception encountered. This indicates a bug in JFlex.
Please consider filing an issue at http://github.com/jflex-de/jflex/issues/new
java.lang.NullPointerException
at jflex.core.NFA.dotFormat(NFA.java:502)
at jflex.core.NFA.writeDot(NFA.java:478)
at jflex.generator.LexGenerator.generate(LexGenerator.java:80)
at jflex.Main.generate(Main.java:320)
at jflex.Main.main(Main.java:336)
It seems that you didn't notice that the StateSet in table can be null while generating the graph.