Make check for byte32 ticket value against 0, safer

AlphaWallet/Market/Coordinators/UniversalLinkCoordinator.swift

@@ -230,7 +230,7 @@ class UniversalLinkCoordinator: Coordinator {
         for i in 0..<indices.count {
             let token: String = balance[Int(indices[i])]
             //all of the indices provided should map to a valid non null ticket
-            if token == Constants.nullTicket {
+            if isZeroBalance(token) {
                 //if null ticket at any index then the deal cannot happen
                 return [String]()
             }

AlphaWallet/Tokens/Helpers/TokenAdaptor.swift

@@ -22,9 +22,7 @@ class TokenAdaptor {
         for (index, item) in balance.enumerated() {
             //id is the value of the bytes32 ticket
             let id = item.balance
-            if id == Constants.nullTicket { // if balance is 0, then skip
-                continue
-            }
+            guard isNonZeroBalance(id) else { continue }
             if let ticketInt = BigUInt(id.drop0x, radix: 16) {
                 let ticket = getTicket(for: ticketInt, index: UInt16(index), in: token)
                 tickets.append(ticket)

AlphaWallet/Tokens/Types/TokenObject.swift

@@ -85,5 +85,9 @@ class TokenObject: Object {
 }
 
 func isNonZeroBalance(_ balance: String) -> Bool {
-    return BigUInt(balance) != 0
+    return !isZeroBalance(balance)
+}
+
+func isZeroBalance(_ balance: String) -> Bool {
+    return BigUInt(balance) == 0
 }