[async] fix async launching without report route

Handle the case where no report route is provided.
Closes #3188

(cherry picked from commit 26d6d95)

async.c

@@ -295,7 +295,7 @@ int async_script_launch(struct sip_msg *msg, struct action* a,
 		return -1;
 	}
 
-	if ( (ctx=shm_malloc(sizeof(async_launch_ctx) + (report_route_param?report_route_param->len:0)))==NULL) {
+	if ( (ctx=shm_malloc(sizeof(async_launch_ctx) + ( (report_route&&report_route_param)?report_route_param->len:0)))==NULL) {
 		LM_ERR("failed to allocate new ctx, forcing sync mode\n");
 		return -1;
 	}
@@ -339,20 +339,22 @@ int async_script_launch(struct sip_msg *msg, struct action* a,
 
 	/* ctx is to be used from this point further */
 
-	ctx->report_route = dup_ref_script_route_in_shm( report_route, 0);
-	if (!ref_script_route_is_valid(ctx->report_route)) {
-		LM_ERR("failed dup resume route -> act in sync mode\n");
-		goto sync;
-	}
+	if (report_route) {
+		ctx->report_route = dup_ref_script_route_in_shm( report_route, 0);
+		if (!ref_script_route_is_valid(ctx->report_route)) {
+			LM_ERR("failed dup resume route -> act in sync mode\n");
+			goto sync;
+		}
 
-	if (report_route_param) {
-		ctx->report_route_param.s = (char *)(ctx+1);
-		ctx->report_route_param.len = report_route_param->len;
-		memcpy(ctx->report_route_param.s, report_route_param->s,
-			report_route_param->len);
-	} else {
-		ctx->report_route_param.s = NULL;
-		ctx->report_route_param.len = 0;
+		if (report_route_param) {
+			ctx->report_route_param.s = (char *)(ctx+1);
+			ctx->report_route_param.len = report_route_param->len;
+			memcpy(ctx->report_route_param.s, report_route_param->s,
+				report_route_param->len);
+		} else {
+			ctx->report_route_param.s = NULL;
+			ctx->report_route_param.len = 0;
+		}
 	}
 
 	if (async_status!=ASYNC_NO_FD) {