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.

src/optionstr.c

@@ -500,7 +500,7 @@ set_string_option(
     if (is_hidden_option(opt_idx))	// don't set hidden option
 	return NULL;
 
-    s = vim_strsave(value);
+    s = vim_strsave(value == NULL ? (char_u *)"" : value);
     if (s != NULL)
     {
 	varp = (char_u **)get_option_varp_scope(opt_idx,

src/version.c

@@ -738,6 +738,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    394,
 /**/
     393,
 /**/