AEC3: Correct the number of render channels in the echo audibility code

Bug: webrtc:11150,chromium:1029707
Change-Id: I4d43bfcd52871a45e7608158bf19c32523976f55
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/161085
Reviewed-by: Gustaf Ullberg <gustaf@webrtc.org>
Commit-Queue: Per Åhgren <peah@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#29971}
diff --git a/modules/audio_processing/aec3/echo_audibility.cc b/modules/audio_processing/aec3/echo_audibility.cc
index db62236..6ae414e 100644
--- a/modules/audio_processing/aec3/echo_audibility.cc
+++ b/modules/audio_processing/aec3/echo_audibility.cc
@@ -88,7 +88,7 @@
 
 bool EchoAudibility::IsRenderTooLow(const BlockBuffer& block_buffer) {
   const int num_render_channels =
-      static_cast<int>(block_buffer.buffer[0].size());
+      static_cast<int>(block_buffer.buffer[0][0].size());
   bool too_low = false;
   const int render_block_write_current = block_buffer.write;
   if (render_block_write_current == render_block_write_prev_) {