mtapi_c: fixed task handling

mtapi_c/src/embb_mtapi_scheduler_t.c

@@ -230,8 +230,8 @@ void embb_mtapi_scheduler_finalize_task(
   if (MTAPI_NULL != task->attributes.complete_func) {
     task->attributes.complete_func(task->handle, MTAPI_NULL);
   }
-  /* delete task if detached */
-  if (MTAPI_TRUE == task->attributes.is_detached) {
+  /* delete task if detached and not in a group */
+  if (MTAPI_NULL == group && MTAPI_TRUE == task->attributes.is_detached) {
     embb_mtapi_task_delete(task, node->task_pool);
   }
 }

mtapi_c/src/embb_mtapi_task_queue_t.c

@@ -146,7 +146,7 @@ mtapi_boolean_t embb_mtapi_task_queue_process(
   if (embb_spin_lock(&that->lock) == EMBB_SUCCESS) {
     idx = that->get_task_position;
     for (ii = 0; ii < that->tasks_available; ii++) {
-      result = process(that->task_buffer[ii], user_data);
+      result = process(that->task_buffer[idx], user_data);
       if (MTAPI_FALSE == result) {
         break;
       }