correct links for network with no sub type

lib/hooks/useNetwork.tsx

 import { useRouter } from 'next/router';
 
-import NETWORKS from 'lib/networks/availableNetworks';
+import findNetwork from 'lib/networks/findNetwork';
 
 export default function useNetwork() {
   const router = useRouter();
-  const selectedNetwork = NETWORKS.find((network) => router.query.network_type === network.type && router.query.network_sub_type === network.subType);
+  const selectedNetwork = findNetwork({
+    network_type: typeof router.query.network_type === 'string' ? router.query.network_type : '',
+    network_sub_type: typeof router.query.network_type === 'string' ? router.query.network_type : undefined,
+  });
   return selectedNetwork;
 }

lib/link/link.ts

 import isBrowser from 'lib/isBrowser';
+import findNetwork from 'lib/networks/findNetwork';
 
 import { ROUTES } from './routes';
 import type { RouteName } from './routes';
@@ -11,7 +12,16 @@ export function link(routeName: RouteName, urlParams?: Record<string, string | u
     return '';
   }
 
+  const network = findNetwork({
+    network_type: urlParams?.network_type || '',
+    network_sub_type: urlParams?.network_sub_type,
+  });
+
   const path = route.pattern.replace(PATH_PARAM_REGEXP, (_, paramName: string) => {
+    if (paramName === 'network_sub_type' && !network?.subType) {
+      return '';
+    }
+
     const paramValue = urlParams?.[paramName];
     return paramValue ? `/${ paramValue }` : '';
   });

lib/networks/findNetwork.ts

+import availableNetworks from 'lib/networks/availableNetworks';
+
+interface Params {
+  network_type: string;
+  network_sub_type?: string;
+}
+
+export default function findNetwork(params: Params) {
+  return availableNetworks.find((network) =>
+    network.type === params.network_type &&
+    network.subType ? network.subType === params.network_sub_type : network.type === params.network_type,
+  );
+}

lib/networks/getAvailablePaths.ts

 import NETWORKS from './availableNetworks';
 
 export default function getAvailablePaths() {
-  return NETWORKS.map(({ type, subType }) => ({ params: { network_type: type, network_sub_type: subType } }));
+  return NETWORKS.map(({ type, subType }) => ({ params: { network_type: type, network_sub_type: subType || 'mainnet' } }));
 }

lib/networks/getNetworkTitle.ts

-import NETWORKS from './availableNetworks';
+import findNetwork from './findNetwork';
 
 export default function getNetworkTitle({ network_type: type, network_sub_type: subType }: {network_type?: string; network_sub_type?: string}) {
-  const currentNetwork = NETWORKS.find(n => n.type === type && n.subType === subType);
+  const currentNetwork = findNetwork({ network_type: type || '', network_sub_type: subType });
   if (currentNetwork) {
     return currentNetwork.name + (currentNetwork.shortName ? ` (${ currentNetwork.shortName })` : '') + ' Explorer';
   }