patch 8.2.2254: Vim9: bool option type is number

Problem:    Vim9: bool option type is number.
Solution:   Have get_option_value() return a different value for bool and
            number options. (closes #7583)
diff --git a/src/spell.c b/src/spell.c
index b474a38..d430566 100644
--- a/src/spell.c
+++ b/src/spell.c
@@ -3813,7 +3813,7 @@
 
     if (no_spell_checking(curwin))
 	return;
-    get_option_value((char_u*)"spl", &dummy, &spl, OPT_LOCAL);
+    (void)get_option_value((char_u*)"spl", &dummy, &spl, OPT_LOCAL);
 
     // Create a new empty buffer in a new window.
     do_cmdline_cmd((char_u *)"new");