Fix Offline Send (#857)

* add offline check to isValidAmount selector

* add z-index fix to AdvancedGas components

* remove z-index mod, use bootstrap class instead

common/components/GasSlider/components/AdvancedGas.tsx

@@ -58,15 +58,15 @@ class AdvancedGas extends React.Component<Props> {
           <GasLimitField includeLabel={false} onlyIncludeLoader={false} />
         </div>
 
-        <div className="col-md-4 col-sm-12">
+        <div className="col-md-4 col-sm-12 col-xs-12">
           <NonceField alwaysDisplay={true} />
         </div>
 
-        <div className="col-md-12">
+        <div className="col-md-12 col-xs-12">
           <DataField />
         </div>
 
-        <div className="col-sm-12">
+        <div className="col-sm-12 col-xs-12">
           <FeeSummary
             render={({ gasPriceWei, gasLimit, fee, usd }) => (
               <span>

common/selectors/transaction/current.ts

@@ -4,6 +4,7 @@ import { AppState } from 'reducers';
 import { isEtherUnit, TokenValue, Wei, Address } from 'libs/units';
 import { getDataExists, getValidGasCost } from 'selectors/transaction';
 import { getCurrentBalance } from 'selectors/wallet';
+import { getOffline } from 'selectors/config';
 
 interface ICurrentValue {
   raw: string;
@@ -42,6 +43,17 @@ const isValidAmount = (state: AppState): boolean => {
   const currentValue = getCurrentValue(state);
   const dataExists = getDataExists(state);
   const validGasCost = getValidGasCost(state);
+  const isOffline = getOffline(state);
+
+  // If value is an empty string, mark as invalid
+  if (!currentValue.raw) {
+    return false;
+  }
+
+  // If offline, assume amount is valid
+  if (isOffline) {
+    return true;
+  }
 
   // We do some wallet validation here.
   // For some reason with MetaMask, sometimes the currentValue.value is not a null