patch 8.1.0320: too much 'incsearch' highlight for pat matching everything

Problem:    Too much 'incsearch' highlight for pattern matching everything.
Solution:   Add the skiplen to the command and remove the line range.
            (Christian Brabandt)  Check for empty pattern earlier.
diff --git a/src/version.c b/src/version.c
index 0c3f87c..d31f9e0 100644
--- a/src/version.c
+++ b/src/version.c
@@ -795,6 +795,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    320,
+/**/
     319,
 /**/
     318,