[fenix] No issue: Fixes ErrorResponse instantiation

app/src/main/java/org/mozilla/fenix/AppRequestInterceptor.kt

@@ -65,7 +65,7 @@ class AppRequestInterceptor(private val context: Context) : RequestInterceptor {
 
         context.components.analytics.metrics.track(Event.ErrorPageVisited(improvedErrorType))
 
-        return RequestInterceptor.ErrorResponse(
+        return RequestInterceptor.ErrorResponse.Content(
             ErrorPages.createErrorPage(
                 context,
                 improvedErrorType,

app/src/test/java/org/mozilla/fenix/AppRequestInterceptorTest.kt

@@ -113,7 +113,9 @@ class AppRequestInterceptorTest {
     }
 
     private fun createActualErrorPage(error: ErrorType): String {
-        return interceptor.onErrorRequest(session = mockk(), errorType = error, uri = null)?.data!!
+        val errorPage = interceptor.onErrorRequest(session = mockk(), errorType = error, uri = null)
+                as RequestInterceptor.ErrorResponse.Content
+        return errorPage.data
     }
 
     private fun createExpectedErrorPage(error: ErrorType, @RawRes html: Int, @RawRes css: Int): String {