Fixed: Corrupt image files when downloading from redirecting Url

closes #3401

src/NzbDrone.Common.Test/Http/HttpClientFixture.cs

@@ -301,6 +301,31 @@ namespace NzbDrone.Common.Test.Http
             ExceptionVerification.ExpectedWarns(1);
         }
 
+        [Test]
+        public void should_not_write_redirect_content_to_stream()
+        {
+            var file = GetTempFilePath();
+
+            using (var fileStream = new FileStream(file, FileMode.Create))
+            {
+                var request = new HttpRequest($"http://{_httpBinHost}/redirect/1");
+                request.AllowAutoRedirect = false;
+                request.ResponseStream = fileStream;
+
+                var response = Subject.Get(request);
+
+                response.StatusCode.Should().Be(HttpStatusCode.Redirect);
+            }
+
+            ExceptionVerification.ExpectedErrors(1);
+
+            File.Exists(file).Should().BeTrue();
+
+            var fileInfo = new FileInfo(file);
+
+            fileInfo.Length.Should().Be(0);
+        }
+
         [Test]
         public void should_send_cookie()
         {

src/NzbDrone.Common/Http/Dispatchers/ManagedHttpDispatcher.cs

@@ -121,9 +121,10 @@ namespace NzbDrone.Common.Http.Dispatchers
                 {
                     try
                     {
-                        if (request.ResponseStream != null)
+                        if (request.ResponseStream != null && httpWebResponse.StatusCode == HttpStatusCode.OK)
                         {
                             // A target ResponseStream was specified, write to that instead.
+                            // But only on the OK status code, since we don't want to write failures and redirects.
                             responseStream.CopyTo(request.ResponseStream);
                         }
                         else