patch 8.2.3083: crash when passing null string to charclass()

Problem:    Crash when passing null string to charclass().
Solution:   Bail out when string pointer is NULL. (Christian Brabandt,
            closes #8498, closes #8260)
diff --git a/src/version.c b/src/version.c
index 532e747..540fa2b 100644
--- a/src/version.c
+++ b/src/version.c
@@ -756,6 +756,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    3083,
+/**/
     3082,
 /**/
     3081,