Use helper method to get web vault url (#1476)

The helper method yields either 1) the configured web vault url or 2)
the configured server url. If neither are configured, null is returned,
which is already handled by defaulting to vault.bitwarden.com

Co-authored-by: Matt Gibson <mdgibson@Matts-MBP.lan>

src/background/runtime.background.ts

@@ -164,7 +164,7 @@ export default class RuntimeBackground {
                 }
                 break;
             case 'authResult':
-                let vaultUrl = this.environmentService.webVaultUrl;
+                let vaultUrl = this.environmentService.getWebVaultUrl();
                 if (vaultUrl == null) {
                     vaultUrl = 'https://vault.bitwarden.com';
                 }