patch 8.1.1186: readdir() allocates list twice

Problem:    readdir() allocates list twice.
Solution:   Remove second allocation.  Also check for zero length.

Author: brammool

src/evalfunc.c

@@ -9324,21 +9324,16 @@ f_readdir(typval_T *argvars, typval_T *rettv)
     }
 #endif
 
-    rettv->vval.v_list = list_alloc();
-    if (!failed && rettv->vval.v_list != NULL)
+    if (!failed && rettv->vval.v_list != NULL && ga.ga_len > 0)
     {
-	++rettv->vval.v_list->lv_refcount;
 	sort_strings((char_u **)ga.ga_data, ga.ga_len);
 	for (i = 0; i < ga.ga_len; i++)
 	{
 	    p = ((char_u **)ga.ga_data)[i];
 	    list_append_string(rettv->vval.v_list, p, -1);
 	}
     }
-    for (i = 0; i < ga.ga_len; i++)
-	vim_free(((char_u **)ga.ga_data)[i]);
-
-    ga_clear(&ga);
+    ga_clear_strings(&ga);
 }
 
 /*

src/version.c

@@ -771,6 +771,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    1186,
 /**/
     1185,
 /**/