[Gradle, JS] Not reset runtimeChunk because it does not affect stacktraces

libraries/tools/kotlin-gradle-plugin/src/common/kotlin/org/jetbrains/kotlin/gradle/targets/js/testing/karma/KotlinKarma.kt

@@ -81,7 +81,7 @@ class KotlinKarma(
     val webpackConfig = KotlinWebpackConfig(
         configDirectory = project.projectDir.resolve("webpack.config.d"),
         optimization = KotlinWebpackConfig.Optimization(
-            runtimeChunk = false,
+            runtimeChunk = null,
             splitChunks = false
         ),
         sourceMaps = true,

libraries/tools/kotlin-gradle-plugin/src/common/kotlin/org/jetbrains/kotlin/gradle/targets/js/webpack/KotlinWebpackConfig.kt

@@ -108,8 +108,8 @@ data class KotlinWebpackConfig(
 
     @Suppress("unused")
     data class Optimization(
-        var runtimeChunk: Any,
-        var splitChunks: Any
+        var runtimeChunk: Any?,
+        var splitChunks: Any?
     ) : Serializable
 
     @Suppress("unused")