patch 8.2.4928: various white space and cosmetic mistakes

Problem:    Various white space and cosmetic mistakes.
Solution:   Change spaces to tabs, improve comments.
diff --git a/src/userfunc.c b/src/userfunc.c
index 081bac1..8d82beb 100644
--- a/src/userfunc.c
+++ b/src/userfunc.c
@@ -2511,7 +2511,7 @@
 	    goto failed;
 	if (fill_partial_and_closure(pt, ufunc, ectx) == FAIL)
 	{
-            vim_free(pt);
+	    vim_free(pt);
 	    goto failed;
 	}
 	ufunc->uf_partial = pt;