Fixed to not throw an exception when password is null.

Author: Adit Sheth

src/Identity/Extensions.Core/src/PasswordValidator.cs

@@ -39,10 +39,10 @@ public PasswordValidator(IdentityErrorDescriber? errors = null)
     /// <returns>The task object representing the asynchronous operation.</returns>
     public virtual Task<IdentityResult> ValidateAsync(UserManager<TUser> manager, TUser user, string? password)
     {
-        ArgumentNullThrowHelper.ThrowIfNull(password);
         ArgumentNullThrowHelper.ThrowIfNull(manager);
         List<IdentityError>? errors = null;
         var options = manager.Options.Password;
+        password ??= "";
         if (string.IsNullOrWhiteSpace(password) || password.Length < options.RequiredLength)
         {
             errors ??= new List<IdentityError>();

src/Identity/test/Identity.Test/PasswordValidatorTest.cs

@@ -24,15 +24,15 @@ public async Task ValidateThrowsWithNullTest()
 
         // Act
         // Assert
-        await Assert.ThrowsAsync<ArgumentNullException>("password", () => validator.ValidateAsync(null, null, null));
         await Assert.ThrowsAsync<ArgumentNullException>("manager", () => validator.ValidateAsync(null, null, "foo"));
     }
 
     [Theory]
-    [InlineData("")]
-    [InlineData("abc")]
-    [InlineData("abcde")]
-    public async Task FailsIfTooShortTests(string input)
+    [InlineData(null)]  
+    [InlineData("")]    
+    [InlineData("abc")] 
+    [InlineData("abcde")] 
+    public async Task FailsIfPasswordIsNullOrTooShort(string input)
     {
         const string error = "Passwords must be at least 6 characters.";
         var manager = MockHelpers.TestUserManager<PocoUser>();