fix(Polar): change some properties to nonnegative

+af_tools/@Polar/Polar.m

@@ -49,9 +49,9 @@ classdef Polar
 
     properties
         airfoil  (1, :) cell
-        reynolds (1, :) double {mustBePositive}
-        mach     (1, :) double {mustBePositive}
-        nCrit    (1, :) double {mustBePositive}
+        reynolds (1, :) double {mustBeNonnegative}
+        mach     (1, :) double {mustBeNonnegative}
+        nCrit    (1, :) double {mustBeNonnegative}
         aoa      (:, :) double {mustBeReal}
         cl       (:, :) double {mustBeReal}
         cd       (:, :) double {mustBeReal}