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.

src/version.c

@@ -794,6 +794,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    320,
 /**/
     319,
 /**/