Adding default properties to NetworkForm (#10682)

Fixes MetaMask/metamask-extension#10681

ui/app/pages/settings/networks-tab/network-form/network-form.component.js

@@ -43,6 +43,14 @@ export default class NetworkForm extends PureComponent {
     isFullScreen: PropTypes.bool,
   };
 
+  static defaultProps = {
+    rpcUrl: '',
+    chainId: '',
+    ticker: '',
+    networkName: '',
+    blockExplorerUrl: '',
+  };
+
   state = {
     rpcUrl: this.props.rpcUrl,
     chainId: this.getDisplayChainId(this.props.chainId),