Drain startup audio on END and validate Opus fixture failures

tools/chatgui/tests/test_stream_view.cpp

@@ -196,7 +196,11 @@ private slots:
                     pcm[2 * i + 1] = static_cast<int16_t>(1500 * std::sin((sampleFrame + i) * 0.13));
                 }
                 sampleFrame += 960;
-                int length = opus_codec_encode(opus.get(), pcm, 960, encoded, sizeof(encoded)); QVERIFY(length > 0);
+                int length = opus_codec_encode(opus.get(), pcm, 960, encoded, sizeof(encoded));
+                if (length <= 0) {
+                    DEBUG_ERROR(DEBUG_CATEGORY_STREAM, "desktop startup fixture Opus encode failed result=%d", length);
+                    return QList<QByteArray>{};
+                }
                 packets.append(QByteArray(reinterpret_cast<const char*>(encoded), length));
             }
             return packets;