chore: fix implicit operand conversion

Ticket: CAAS-7

Author: Gautam2305

modules/sdk-core/src/bitgo/wallet/wallet.ts

@@ -2200,7 +2200,7 @@ export class Wallet implements IWallet {
         PrebuildTransactionResult
       ];
     } catch (err) {
-      if (err || (err instanceof Error && err.message.includes('unable to decrypt keychain'))) {
+      if (err !== null || (err instanceof Error && err.message.includes('unable to decrypt keychain'))) {
         const error: Error & { code?: string } = new Error(
           `unable to decrypt keychain with the given wallet passphrase`
         );