Throw on NaN values to Baggy.roll/.pick/.grab

Fixes RT#131270: https://rt.perl.org/Ticket/Display.html?id=131270

src/core/Baggy.pm

@@ -519,6 +519,8 @@ my role Baggy does QuantHash {
     }
 
     method !ROLLPICKGRABN(\count, @pairs, :$keep) { # N times
+        nqp::istype(count, Int)
+        || X::Invalid::ComputedValue.new(:name<count>, :value(count)).throw;
         Seq.new(class :: does Iterator {
             has Int $!total;
             has int $!elems;