try fix null ref exception in tests

Author: sierpinskid

Packages/StreamVideo/Runtime/Core/LowLevelClient/RtcSession.cs

@@ -393,7 +393,10 @@ public async Task StopAsync(string reason = "")
                 {
                     // Trace leave call before leaving the call. Otherwise, stats are not send because SFU WS disconnects
                     _sfuTracer?.Trace(PeerConnectionTraceKey.LeaveCall, new { SessionId = SessionId, Reason = reason });
-                    await _statsSender.SendFinalStatsAsync();
+                    if (_statsSender != null) // This was null in tests
+                    {
+                        await _statsSender.SendFinalStatsAsync();
+                    }
                 }
                 catch (Exception e)
                 {

Packages/StreamVideo/Runtime/Core/Stats/WebRtcStatsSender.cs

@@ -76,6 +76,11 @@ internal WebRtcStatsSender(RtcSession rtcSession, IWebRtcStatsCollector webRtcSt
 
         private async Task CollectAndSend()
         {
+            if (_rtcSession.ActiveCall == null)
+            {
+                return;
+            }
+            
             var subscriberStatsJson = await _webRtcStatsCollector.GetSubscriberStatsJsonAsync();
             var publisherStatsJson = await _webRtcStatsCollector.GetPublisherStatsJsonAsync();
             var rtcStatsJson = await _webRtcStatsCollector.GetRtcStatsJsonAsync();