patch 8.0.0365: might free a dict item that wasn't allocated

Problem:    Might free a dict item that wasn't allocated.
Solution:   Call dictitem_free(). (Nikolai Pavlov)  Use this for
            b:changedtick.
diff --git a/src/dict.c b/src/dict.c
index 07d1000..7074305 100644
--- a/src/dict.c
+++ b/src/dict.c
@@ -88,8 +88,7 @@
 	     * something recursive causing trouble. */
 	    di = HI2DI(hi);
 	    hash_remove(&d->dv_hashtab, hi);
-	    clear_tv(&di->di_tv);
-	    vim_free(di);
+	    dictitem_free(di);
 	    --todo;
 	}
     }