Assertion due to deleted account during incoming call in PJSUA2 (pjsi…

…p#4024)

(cherry picked from commit 0e0573d)

pjsip/src/pjsua-lib/pjsua_call.c

@@ -2153,7 +2153,7 @@ pj_bool_t pjsua_call_on_incoming(pjsip_rx_data *rdata)
      */
     if (dlg->mod_data[pjsua_var.mod.id] == NULL) {
         /* In PJSUA2, on_incoming_call() may be called from 
-         * on_media_transport_created() hence this might already set
+         * on_create_media_transport() hence this might already set
          * to allow notification about fail events via on_call_state() and
          * on_call_tsx_state().
          */
@@ -2179,7 +2179,12 @@ pj_bool_t pjsua_call_on_incoming(pjsip_rx_data *rdata)
          * otherwise hangup the call with 480
          */
         if (pjsua_var.ua_cfg.cb.on_incoming_call) {
-            pjsua_var.ua_cfg.cb.on_incoming_call(acc_id, call_id, rdata);
+            /* For PJSUA2, avoid invoking this callback again when it has been
+             * invoked from on_create_media_transport().
+             */
+            if (call->incoming_data) {
+                pjsua_var.ua_cfg.cb.on_incoming_call(acc_id, call_id, rdata);
+            }
 
             /* Notes:
              * - the call might be reset when it's rejected or hangup
@@ -2190,6 +2195,7 @@ pj_bool_t pjsua_call_on_incoming(pjsip_rx_data *rdata)
              * answer/hangup should have been delayed (see #1923), 
              * so let's process the answer/hangup now.
              */
+
             if (call->async_call.call_var.inc_call.hangup) {
                 process_pending_call_hangup(call);
             } else if (call->med_ch_cb == NULL && call->inv) {