Fix to not crash when VideoEncoderFactory fails to create encoder

Bug: webrtc:13082
Change-Id: I5f1cfa7db6259e71ce3fc18281a3d084c32911ea
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/257923
Reviewed-by: Artem Titov <titovartem@webrtc.org>
Reviewed-by: Erik Språng <sprang@webrtc.org>
Commit-Queue: Daniel.L (Byoungchan) Lee <daniel.l@hpcnt.com>
Cr-Commit-Position: refs/heads/main@{#36501}

test/video_encoder_nullable_proxy_factory.h

@@ -0,0 +1,45 @@
+/*
+ *  Copyright (c) 2022 The WebRTC project authors. All Rights Reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+#ifndef TEST_VIDEO_ENCODER_NULLABLE_PROXY_FACTORY_H_
+#define TEST_VIDEO_ENCODER_NULLABLE_PROXY_FACTORY_H_
+
+#include <memory>
+#include <vector>
+
+#include "api/video_codecs/video_encoder.h"
+#include "api/video_codecs/video_encoder_factory.h"
+#include "test/video_encoder_proxy_factory.h"
+
+namespace webrtc {
+namespace test {
+
+class VideoEncoderNullableProxyFactory final : public VideoEncoderProxyFactory {
+ public:
+  explicit VideoEncoderNullableProxyFactory(
+      VideoEncoder* encoder,
+      EncoderSelectorInterface* encoder_selector)
+      : VideoEncoderProxyFactory(encoder, encoder_selector) {}
+
+  ~VideoEncoderNullableProxyFactory() override = default;
+
+  std::unique_ptr<VideoEncoder> CreateVideoEncoder(
+      const SdpVideoFormat& format) override {
+    if (!encoder_) {
+      return nullptr;
+    }
+    return VideoEncoderProxyFactory::CreateVideoEncoder(format);
+  }
+};
+
+}  // namespace test
+}  // namespace webrtc
+
+#endif  // TEST_VIDEO_ENCODER_NULLABLE_PROXY_FACTORY_H_