Coorectly parse ETag value

Author: ronaldbarendse

src/Umbraco.StorageProviders.AzureBlob/AzureBlobFileSystemMiddleware.cs

@@ -164,7 +164,12 @@ private async Task HandleRequestAsync(HttpContext context, RequestDelegate next)
                 };
 
             responseHeaders.LastModified = properties.Value.LastModified;
-            responseHeaders.ETag = new EntityTagHeaderValue(properties.Value.ETag.ToString("H"));
+
+            if (EntityTagHeaderValue.TryParse(properties.Value.ETag.ToString("H"), out EntityTagHeaderValue entityTagHeaderValue))
+            {
+                responseHeaders.ETag = entityTagHeaderValue;
+            }
+
             responseHeaders.Append(HeaderNames.Vary, "Accept-Encoding");
 
             var requestHeaders = request.GetTypedHeaders();