update fnecore submodule; send TDU 4 times at call release;

dvmconsole/FneSystemBase.P25.cs

@@ -77,7 +77,13 @@ namespace dvmconsole
                 LCO = P25Defines.LC_GROUP
             };
 
-            SendP25TDU(callData, grantDemand);
+            if (grantDemand)
+                SendP25TDU(callData, grantDemand);
+            else
+            {
+                for (int i = 0; i < 4; i++)
+                    SendP25TDU(callData, false);
+            }
         }
 
         /// <summary>

fnecore

@@ -1 +1 @@
-Subproject commit 11206a353ff36aa503cc5955432838a14214b626
+Subproject commit 89ca6012ce9aa60d26283084fdb1a45a686e526f