Unit Attack: fixed issues arising from displayed items potentially not equally available items

Since there were weapons included that weren't shown, it was possible for the best
weapon selection to be a hidden one (in which case, the initial selection would be
wrong, and it was possible for the returned index to point to a hidden, disabled
weapon.

This resolves both issues by excluding these disabled attacks from the weapon choices
list altogether. They aren't considered when calculating the best attack either.

mouse_handler::fill_weapon_choices is also used in mouse_handler::attack_enemy_, but
I don't foresee this change should cause any issues there, since you aren't supposed
to be able to actually attack with disabled weapons anyway.

changelog.md

@@ -242,6 +242,10 @@
      custom caption= is specified (fixes #3211).
    * do_not_list=yes units are no longer excluded from the debug mode-only
      Create Unit dialog.
+   * Fixed a rare issue where disabled attacks could cause the wrong attack to
+     be initially selected in the Unit Attack dialog. This bug also had the
+     potential to cause units to the wrong attack when  engaging or viewing
+     damage calculations.
 
 ## Version 1.13.12
  ### Security fixes

src/gui/dialogs/unit_attack.cpp

@@ -120,11 +120,6 @@ void unit_attack::pre_show(window& window)
 		const attack_type& defender_weapon = defender.weapon ?
 			*defender.weapon : *no_weapon;
 
-		// Don't show if the attacker's weapon has at least one active "disable" special.
-		if(attacker.disable) {
-			continue;
-		}
-
 		const color_t a_cth_color = game_config::red_to_green(attacker.chance_to_hit);
 		const color_t d_cth_color = game_config::red_to_green(defender.chance_to_hit);
 
@@ -197,8 +192,11 @@ void unit_attack::pre_show(window& window)
 		weapon_list.add_row(data);
 	}
 
-	const int last_item = weapon_list.get_item_count() - 1;
-	weapon_list.select_row(std::min(best_weapon_, last_item));
+	// If these two aren't the same size, we can't use list selection incides
+	// to access to weapons list!
+	assert(weapons_.size() == weapon_list.get_item_count());
+
+	weapon_list.select_row(best_weapon_);
 }
 
 void unit_attack::post_show(window& window)

src/mouse_events.cpp

@@ -950,6 +950,11 @@ int mouse_handler::fill_weapon_choices(
 		if(attacker->attacks()[i].attack_weight() > 0) {
 			battle_context bc(pc_.gamestate().board_.units_, attacker->get_location(), defender->get_location(), i);
 
+			// Don't include if the attacker's weapon has at least one active "disable" special.
+			if(bc.get_attacker_stats().disable) {
+				continue;
+			}
+
 			if(!bc_vector.empty() && bc.better_attack(bc_vector[best], 0.5)) {
 				// as some weapons can be hidden, i is not a valid index into the resulting vector
 				best = bc_vector.size();