Proper handling confirmations

Trust/EtherClient/ChainState.swift

@@ -56,4 +56,10 @@ class ChainState {
             }
         }
     }
+
+    func confirmations(fromBlock: Int) -> Int? {
+        guard latestBlock != 0 else { return nil }
+        return max(0, latestBlock - fromBlock)
+    }
+
 }

Trust/Transactions/ViewModels/TransactionCellViewModel.swift

@@ -18,15 +18,15 @@ struct TransactionCellViewModel {
         self.chainState = chainState
     }
 
-    var confirmations: Int {
-        return max(chainState.latestBlock - Int(transaction.blockNumber), 0)
+    var confirmations: Int? {
+        return chainState.confirmations(fromBlock: transaction.blockNumber)
     }
 
     var state: TransactionState {
         if transaction.isError {
             return .error
         }
-        if confirmations <= 0 && chainState.latestBlock >= transaction.blockNumber {
+        if confirmations == 0 {
             return .pending
         }
         return .completed

Trust/Transactions/ViewModels/TransactionViewModel.swift

@@ -83,8 +83,10 @@ struct TransactionViewModel {
     }
 
     var confirmation: String {
-        let confirmation = chainState.latestBlock - Int(transaction.blockNumber)
-        return String(max(0, confirmation))
+        guard let confirmation = chainState.confirmations(fromBlock: transaction.blockNumber) else {
+            return "--"
+        }
+        return String(confirmation)
     }
 
     var blockNumber: String {