patch 8.1.2119: memory access error for empty string

Problem:    memory access error for empty string when 'encoding' is a single
            byte encoding.
Solution:   Check for empty string when getting the length. (Dominique Pelle,
            closes #5021, closes #5007)

src/version.c

@@ -753,6 +753,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    2119,
 /**/
     2118,
 /**/