Make JavaScriptEncoder optional and Fallback to JavaScriptEncoder.Default (#918)

* make JavascriptEncoder optional parameter to prevent crash when no encoder is available.

CHANGELOG.md

@@ -2,6 +2,9 @@
 
 ## Version 2.8.0-beta1
 - [Fix: Add `IJavaScriptSnippet` service interface and update the `IServiceCollection` extension to register it for `JavaScriptSnippet`.](https://github.com/microsoft/ApplicationInsights-aspnetcore/issues/890)
+- [Make JavaScriptEncoder optional and Fallback to JavaScriptEncoder.Default.](https://github.com/microsoft/ApplicationInsights-aspnetcore/pull/918)
+
+## Version 2.7.1
 - [Fix - ApplicationInsights StartupFilter should not swallow exceptions from downstream ApplicationBuilder.](https://github.com/microsoft/ApplicationInsights-aspnetcore/issues/897)
 
 ## Version 2.7.0

src/Microsoft.ApplicationInsights.AspNetCore/JavaScriptSnippet.cs

@@ -41,12 +41,12 @@
             TelemetryConfiguration telemetryConfiguration,
             IOptions<ApplicationInsightsServiceOptions> serviceOptions,
             IHttpContextAccessor httpContextAccessor,
-            JavaScriptEncoder encoder)
+            JavaScriptEncoder encoder = null)
         {
             this.telemetryConfiguration = telemetryConfiguration;
             this.httpContextAccessor = httpContextAccessor;
             this.enableAuthSnippet = serviceOptions.Value.EnableAuthenticationTrackingJavaScript;
-            this.encoder = encoder;
+            this.encoder = (encoder == null) ? JavaScriptEncoder.Default : encoder;
         }
 
         /// <summary>