ProfileViewer: Ignore empty samples

Sometimes we get empty samples in a profile. I'm not sure why that
happens, but let's just ignore them for now.

DevTools/ProfileViewer/Profile.cpp

@@ -28,10 +28,15 @@ Profile::Profile(const JsonArray& json)
 
  Sample sample;
  sample.timestamp = sample_object.get("timestamp").to_number<u64>();
- sample.in_kernel = sample_object.get("frames").as_array().at(1).as_object().get("address").to_number<u32>() < (8 * MB);
 
  auto frames_value = sample_object.get("frames");
  auto& frames_array = frames_value.as_array();
+
+ if (frames_array.size() < 2)
+ continue;
+
+ sample.in_kernel = frames_array.at(1).as_object().get("address").to_number<u32>() < (8 * MB);
+
  for (int i = frames_array.size() - 1; i >= 1; --i) {
  auto& frame_value = frames_array.at(i);
  auto& frame_object = frame_value.as_object();