Fix switch weapon addAction with nothing in hands

The addAction click was doing an animation without switching when the
player had a primary or melee on back but nothing in hands.

Probably present in vanilla too, will check later.

SQF/dayz_code/actions/player_switchWeapon_action.sqf

@@ -1 +1,9 @@
-1 call dz_fn_switchWeapon;
+if (primaryWeapon player == "") then {
+	if (dayz_onBack in MeleeWeapons) then {
+		4 call dz_fn_switchWeapon; // Melee
+	} else {
+		2 call dz_fn_switchWeapon; // Rifle
+	};
+} else {
+	1 call dz_fn_switchWeapon;
+};