Yang parser tries to process unknown character like '#' as a Yang statement and crashes with NPE

Yang parser tries to process unknown character like '#' as a Yang statement and crashes with NullPointerException. This needs to be handled and proper exception thrown.

Example YANG snippet:

module aug-second {
.
.
.

1. With Bug present, this works just because tf is not involved.
   augment "/ts:target" { . . . }

}

Error stack:

java.lang.NullPointerException
13:12:47 at org.opendaylight.yangtools.yang.parser.stmt.rfc6020.YangStatementSourceImpl.writePreLinkage(YangStatementSourceImpl.java:101)
13:12:47 at org.opendaylight.yangtools.yang.parser.stmt.reactor.SourceSpecificContext.loadStatements(SourceSpecificContext.java:349)
13:12:47 at org.opendaylight.yangtools.yang.parser.stmt.reactor.BuildGlobalContext.loadPhaseStatements(BuildGlobalContext.java:241)
13:12:47 at org.opendaylight.yangtools.yang.parser.stmt.reactor.BuildGlobalContext.buildEffective(BuildGlobalContext.java:199)
13:12:47 at org.opendaylight.yangtools.yang.parser.stmt.reactor.CrossSourceStatementReactor$BuildAction.buildEffective(CrossSourceStatementReactor.java:128)
13:12:47 at org.opendaylight.yangtools.yang.stmt.Bug6150Test.effectiveAugmentFirstTest(Bug6150Test.java:39)
13:12:47 at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
13:12:47 at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
13:12:47 at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)