patch 8.2.4262: some search tests fail

Problem:    Some search tests fail.
Solution:   Use a better way to reject searching for the Visual area.
diff --git a/src/regexp.c b/src/regexp.c
index 9505765..29c2d38 100644
--- a/src/regexp.c
+++ b/src/regexp.c
@@ -1268,7 +1268,7 @@
     colnr_T	curswant;
 
     // Check if the buffer is the current buffer and not using a string.
-    if (rex.reg_buf != curbuf || VIsual.lnum == 0 || rex.reg_maxline == 0)
+    if (rex.reg_buf != curbuf || VIsual.lnum == 0 || !REG_MULTI)
 	return FALSE;
 
     if (VIsual_active)