System.ArgumentNullException

I keep getting this exception when I try to run my code:

System.ArgumentNullException: Value cannot be null. Parameter name: String at System.Number.StringToNumber (System.String str, System.Globalization.NumberStyles options, System.Number+NumberBuffer& number, System.Globalization.NumberFormatInfo info, System.Boolean parseDecimal) [0x00054] in /builddir/build/BUILD/mono-4.8.0/mcs/class/referencesource/mscorlib/system/number.cs:1074 at System.Number.ParseInt32 (System.String s, System.Globalization.NumberStyles style, System.Globalization.NumberFormatInfo info) [0x00014] in /builddir/build/BUILD/mono-4.8.0/mcs/class/referencesource/mscorlib/system/number.cs:745 at System.Int32.Parse (System.String s) [0x00000] in /builddir/build/BUILD/mono-4.8.0/mcs/class/referencesource/mscorlib/system/int32.cs:120 at Treehouse.CodeChallenges.Program.Main () [0x00010] in <3ecdb2bf57d24db7832c050d1b856030>:0 at MonoTester.Run () [0x00095] in MonoTester.cs:86 at MonoTester.Main (System.String[] args) [0x00013] in MonoTester.cs:28

I'm honestly just confused...

using System;

namespace Treehouse.CodeChallenges
{
    class Program
    {
        static void Main ()
        {
            while (true)
            {
                Console.Write("Enter the number of times to print \"Yay!\": ");
                var entry = Console.ReadLine();

                try
                {
                    var numTimes = int.Parse(entry);
                    if (numTimes <= 0)
                    {
                        Console.WriteLine("You must enter a positive number.");
                        continue;
                    }
                    while (numTimes > 0)
                    {
                        Console.WriteLine("Yay!");
                        numTimes--;
                    }
                }

                catch (FormatException)
                {
                    Console.WriteLine("You must enter a whole number.");
                }
            }
        }
    }
}