Fix return value of hook calls that have no handlers.

For this case, the return value is always true.

testing/btest/Baseline/language.hook/out

@@ -3,6 +3,7 @@ myhook return F
 myhook return T
 myhook, &priority=5, [a=37, b=goobye world]
 F
+T
 myhook3, 8
 T
 myhook4, 2