Fix anon users can't zap other anon users

api/resolvers/item.js

@@ -764,7 +764,8 @@ export default {
         user = invoice.user
       }
 
-      // disallow self tips
+      // disallow self tips except anons
+      if (user.id !== ANON_USER_ID) {
         const [item] = await models.$queryRawUnsafe(`
         ${SELECT}
         FROM "Item"
@@ -772,6 +773,7 @@ export default {
         if (item) {
           throw new GraphQLError('cannot zap your self', { extensions: { code: 'BAD_INPUT' } })
         }
+      }
 
       const calls = [
         models.$queryRaw`SELECT item_act(${Number(id)}::INTEGER, ${user.id}::INTEGER, 'TIP', ${Number(sats)}::INTEGER)`