Yecht crashes on weird data

jruby -ryaml -e "p YAML.load_file('config_yaml_spec.rb')"

String.java:397:in `checkBounds': java.lang.StringIndexOutOfBoundsException: String index out of range: -1
        from String.java:442:in `<init>'
        from RubyErrHandler.java:28:in `handle'
        from TokenScanner.java:19:in `error'
        from DefaultYAMLParser.java:803:in `yyerror'
        from DefaultYAMLParser.java:329:in `yyparse'
        from Parser.java:290:in `yechtparse'
        from Parser.java:284:in `parse'
        from YParser.java:152:in `load'
        from org/yecht/ruby/YParser$s_method_0_1$RUBYINVOKER$load.gen:-1:in `call'
        from JavaMethod.java:631:in `call'
        from DynamicMethod.java:186:in `call'
        from CachingCallSite.java:309:in `cacheAndCall'
        from CachingCallSite.java:148:in `call'
        from CallOneArgNode.java:57:in `interpret'
        from LocalAsgnNode.java:123:in `interpret'
        from NewlineNode.java:104:in `interpret'
        from InterpretedMethod.java:173:in `call'
        from DefaultMethod.java:171:in `call'
        from CachingCallSite.java:309:in `cacheAndCall'
        from CachingCallSite.java:148:in `call'
        from FCallOneArgNode.java:36:in `interpret'
        from NewlineNode.java:104:in `interpret'
        from InterpretedBlock.java:317:in `evalBlockBody'
        from InterpretedBlock.java:268:in `yield'
        from Block.java:194:in `yield'
        from RubyIO.java:1092:in `open'
        from org/jruby/RubyIO$s_method_0_2$RUBYFRAMEDINVOKER$open.gen:-1:in `call'
        from DynamicMethod.java:190:in `call'
        from CachingCallSite.java:319:in `cacheAndCall'
        from CachingCallSite.java:157:in `callBlock'
        from CachingCallSite.java:162:in `call'
        from CallOneArgBlockNode.java:60:in `interpret'
        from NewlineNode.java:104:in `interpret'
        from InterpretedMethod.java:173:in `call'
        from DefaultMethod.java:171:in `call'
        from CachingCallSite.java:309:in `cacheAndCall'
        from CachingCallSite.java:148:in `call'
        from -e:1:in `__file__'
        from -e:-1:in `load'
        from Ruby.java:632:in `runScript'
        from Ruby.java:550:in `runNormally'
        from Ruby.java:396:in `runFromMain'
        from Main.java:272:in `run'
        from Main.java:117:in `run'
        from Main.java:97:in `main'