patch 8.2.0171: Coverity warning for using uninitialized buffer

Problem:    Coverity warning for using uninitialized buffer.
Solution:   Check the skip flag.
diff --git a/src/userfunc.c b/src/userfunc.c
index 1878eab..474812c 100644
--- a/src/userfunc.c
+++ b/src/userfunc.c
@@ -2188,7 +2188,7 @@
     name = alloc(len + lead + extra + 1);
     if (name != NULL)
     {
-	if (lead > 0 || vim9script)
+	if (!skip && (lead > 0 || vim9script))
 	{
 	    name[0] = K_SPECIAL;
 	    name[1] = KS_EXTRA;