patch 8.2.2295: incsearch does not detect empty pattern properly

Problem:    Incsearch does not detect empty pattern properly.
Solution:   Return magic state when skipping over a pattern. (Christian
            Brabandt, closes #7612, closes #6420)
diff --git a/src/search.c b/src/search.c
index 6305b58..3a4d458 100644
--- a/src/search.c
+++ b/src/search.c
@@ -1342,7 +1342,7 @@
 	     */
 	    ps = strcopy;
 	    p = skip_regexp_ex(pat, search_delim, magic_isset(),
-							       &strcopy, NULL);
+							&strcopy, NULL, NULL);
 	    if (strcopy != ps)
 	    {
 		// made a copy of "pat" to change "\?" to "?"