fix: properly check if metamask is installed

wallets/cosmos-extension-metamask/src/extension/main-wallet.ts

@@ -3,6 +3,7 @@ import { MainWalletBase } from '@cosmos-kit/core';
 
 import { ChainCosmosExtensionMetamaskSnap } from './chain-wallet';
 import { CosmosExtensionClient } from './client';
+import { isMetamaskInstalled } from './utils';
 
 export class CosmosMetamaskExtensionWallet extends MainWalletBase {
   constructor(walletInfo: Wallet) {
@@ -12,7 +13,8 @@ export class CosmosMetamaskExtensionWallet extends MainWalletBase {
   async initClient() {
     this.initingClient();
     try {
-      this.initClientDone(new CosmosExtensionClient());
+      const installed = await isMetamaskInstalled();
+      this.initClientDone(installed ? new CosmosExtensionClient() : undefined);
     } catch (error) {
       this.initClientError(error);
     }

wallets/cosmos-extension-metamask/src/extension/utils.ts

@@ -1,17 +1,38 @@
 import { ClientNotExistError } from '@cosmos-kit/core';
 import { CosmosSnap } from '@cosmsnap/snapper';
 
+interface MetamaskWindow {
+  ethereum?: {
+    isMetaMask?: boolean;
+  };
+}
+
 interface SnapWindow {
   cosmos?: CosmosSnap;
 }
 
+export const isMetamaskInstalled = async (): Promise<boolean> => {
+  if (typeof window === 'undefined') {
+    return false;
+  }
+
+  const ethereum = (window as MetamaskWindow).ethereum;
+  return Boolean(ethereum?.isMetaMask);
+};
+
 export const getSnapProviderFromExtension: () => Promise<
   CosmosSnap | undefined
 > = async () => {
   if (typeof window === 'undefined') {
     return void 0;
   }
 
+  // Check if MetaMask is installed first
+  const hasMetaMask = await isMetamaskInstalled();
+  if (!hasMetaMask) {
+    throw ClientNotExistError;
+  }
+
   const cosmos = (window as SnapWindow).cosmos;
 
   if (cosmos) {