fix: crash on reverse resolving post subdomain transfer

src/naming/main.cairo

@@ -203,6 +203,9 @@ mod Naming {
         fn domain_to_address(
             self: @ContractState, domain: Span<felt252>, hint: Span<felt252>
         ) -> ContractAddress {
+            if domain.len() == 0 {
+                return ContractAddressZeroable::zero();
+            }
             let (resolver, parent_length) = self.domain_to_resolver(domain);
             // if there is a resolver starting from the top
             if (resolver != ContractAddressZeroable::zero()) {
@@ -305,9 +308,11 @@ mod Naming {
                 //     self.domain_to_address(domain, array![].span()) == address,
                 //     'domain not pointing back'
                 // );
+                println!("echo: {:?}", domain);
                 if self.domain_to_address(domain, array![].span()) != address {
                     return array![].span();
                 }
+                println!("hey");
                 domain
             }
         }

src/tests/naming/test_abuses.cairo

@@ -409,3 +409,54 @@ fn test_buy_empty_domain() {
             0
         );
 }
+
+
+#[test]
+#[available_gas(2000000000)]
+fn test_subdomain_reverse() {
+    // setup
+    let (eth, pricing, identity, naming) = deploy();
+    let alpha = contract_address_const::<0x123>();
+    let bravo = contract_address_const::<0x456>();
+    let charlie = contract_address_const::<0x789>();
+
+    // we mint the ids
+    set_contract_address(alpha);
+    identity.mint(1);
+    set_contract_address(bravo);
+    identity.mint(2);
+    set_contract_address(charlie);
+    identity.mint(3);
+
+    set_contract_address(alpha);
+    let aller: felt252 = 35683102;
+
+    // we check how much a domain costs
+    let (_, price) = pricing.compute_buy_price(5, 365);
+
+    // we allow the naming to take our money
+    eth.approve(naming.contract_address, price);
+
+    // we buy with no resolver, no sponsor, no discount and empty metadata
+    naming
+        .buy(1, aller, 365, ContractAddressZeroable::zero(), ContractAddressZeroable::zero(), 0, 0);
+
+    let subdomain = array![aller, aller].span();
+
+    // we transfer aller.aller.stark to id2
+    naming.transfer_domain(subdomain, 2);
+
+    // and make sure the owner has been updated
+    assert(naming.domain_to_id(subdomain) == 2, 'owner not updated correctly');
+    set_contract_address(bravo);
+    let result = naming.address_to_domain(bravo, array![].span());
+    assert(result == array![].span(), 'unexpected result');
+    // we then set this subdomain as main domain and ensures reverse resolving works
+    identity.set_main_id(2);
+    let result = naming.address_to_domain(bravo, array![].span());
+    assert(result == subdomain, 'unexpected result');
+    // before transfering this subdomain
+    naming.transfer_domain(subdomain, 3);
+    let result = naming.address_to_domain(bravo, array![].span());
+    assert(result == array![].span(), 'unexpected result');
+}