Events with no expiration declared being set to zero expirationOffset during package assembly

Had a problem with events being expired immediately on being inserted. These events have no @expiration declaration. Tracing and debugging led to this line:

ReteooRuleBase, line 477:
node.setExpirationOffset( Math.max( node.getExpirationOffset(), typeDeclaration.getExpirationOffset()+1 ) );

Since neither the type and its supertype have expirations declared, getExpirationOffset() returns -1 in both cases. Max(-1, -1 + 1) == 0, so the event is assigned an expiration of zero.

Should make sure not to set the expiration when both are already -1.