Fix snapshot handling when converting 0.7 demo snapshot failed

Only prevent demo recording instead of ignoring most of the snapshot by returning early when coverting the snapshot for demo recording failed.

src/engine/client/client.cpp

@@ -2006,17 +2006,19 @@ void CClient::ProcessServerPacket(CNetChunk *pPacket, int Conn, bool Dummy)
 							if(DemoSnapSize < 0)
 							{
 								dbg_msg("sixup", "demo snapshot failed. error=%d", DemoSnapSize);
-								return;
 							}
 						}
 
-						// add snapshot to demo
-						for(auto &DemoRecorder : m_aDemoRecorder)
+						if(DemoSnapSize >= 0)
 						{
-							if(DemoRecorder.IsRecording())
+							// add snapshot to demo
+							for(auto &DemoRecorder : m_aDemoRecorder)
 							{
-								// write snapshot
-								DemoRecorder.RecordSnapshot(GameTick, IsSixup() ? pSnapSeven : pTmpBuffer3, DemoSnapSize);
+								if(DemoRecorder.IsRecording())
+								{
+									// write snapshot
+									DemoRecorder.RecordSnapshot(GameTick, IsSixup() ? pSnapSeven : pTmpBuffer3, DemoSnapSize);
+								}
 							}
 						}
 					}