patch 8.2.0394: Coverity complains about using NULL pointer

Problem:    Coverity complains about using NULL pointer.
Solution:   Use empty string when option value is NULL.
diff --git a/src/version.c b/src/version.c
index b0497a5..717ca66 100644
--- a/src/version.c
+++ b/src/version.c
@@ -739,6 +739,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    394,
+/**/
     393,
 /**/
     392,