fix(gradient): remove invalid decision branches (#3226)

Co-authored-by: pengyiqiang <pengyiqiang@xiaomi.com>

src/draw/sw/lv_draw_sw_gradient.c

@@ -86,8 +86,6 @@ static lv_grad_t * next_in_cache(lv_grad_t * item)
 
     if(item == NULL)
         return (lv_grad_t *)LV_GC_ROOT(_lv_grad_cache_mem);
-    if(item == NULL)
-        return NULL;
 
     size_t s = get_cache_item_size(item);
     /*Compute the size for this cache item*/