删除非必要assert，否则可能导致demo卡主

demo/demo_stack.c

@@ -200,7 +200,6 @@ static void demo_stack_struct(void)
         }
     }
 
-    stack->_destory(stack);
     stack_free(&stack);
 }
 

src/stack.c

@@ -124,7 +124,6 @@ static uint32_t stack_capacity(struct _stack* self)
 static bool stack_clear(struct _stack* self)
 {
     assert(self != NULL);
-    assert(self->_head != NULL);
     if (self->empty(self))
     {
         return true;