fix: Fix test warnings (async void -> async Task, nullable arrays)

Author: birdnamoo

src/FunctionX.Tests/FxCountIfTests.cs

@@ -140,7 +140,7 @@ public async Task TestCountIf_MixedTypes_OnlyCountsAppropriateTypes()
         // Arrange
         var parameters = new Dictionary<string, object?>
         {
-            { "mixed", new object[] { 1, "5", 10, "text", 15, null } }
+            { "mixed", new object?[] { 1, "5", 10, "text", 15, null } }
         };
 
         // Act

src/FunctionX.Tests/FxMinTests.cs

@@ -7,7 +7,7 @@ namespace FunctionX.Tests;
 public class FxMinTests
 {
     [Fact]
-    public async void TestEvaluateMinWithConstants()
+    public async Task TestEvaluateMinWithConstants()
     {
         // Arrange
         var results = new Dictionary<string, object?>();
@@ -20,7 +20,7 @@ public async void TestEvaluateMinWithConstants()
     }
 
     [Fact]
-    public async void TestEvaluateMinWithVariable()
+    public async Task TestEvaluateMinWithVariable()
     {
         // Arrange
         var results = new Dictionary<string, object?>
@@ -37,7 +37,7 @@ public async void TestEvaluateMinWithVariable()
 
 
     [Fact]
-    public async void TestEvaluateMinWithEmptyArray()
+    public async Task TestEvaluateMinWithEmptyArray()
     {
         // Arrange
         var results = new Dictionary<string, object?>
@@ -54,7 +54,7 @@ public async void TestEvaluateMinWithEmptyArray()
 
 
     [Fact]
-    public async void TestEvaluateMinWithNullValues()
+    public async Task TestEvaluateMinWithNullValues()
     {
         // Arrange
         var results = new Dictionary<string, object?>
@@ -71,7 +71,7 @@ public async void TestEvaluateMinWithNullValues()
     }
 
     [Fact]
-    public async void TestEvaluateMinWithNaN()
+    public async Task TestEvaluateMinWithNaN()
     {
         // Arrange
         var results = new Dictionary<string, object?>

src/FunctionX.Tests/FxSumIfTests.cs

@@ -162,7 +162,7 @@ public async Task TestSumIf_MixedDataTypes_OnlySumsNumbers()
         var parameters = new Dictionary<string, object?>
         {
             { "criteria_data", new object[] { 1, 2, 3, 4, 5 } },
-            { "sum_data", new object[] { 10, "text", 30, null, 50 } }
+            { "sum_data", new object?[] { 10, "text", 30, null, 50 } }
         };
 
         // Act