backups: validate mountOptions is an object for managed providers

src/backups.js

@@ -454,6 +454,8 @@ async function setupStorage(storageConfig, hostPath) {
 
     if (!mounts.isManagedProvider(storageConfig.provider)) return null;
 
+    if (!storageConfig.mountOptions || typeof storageConfig.mountOptions !== 'object') throw new BoxError(BoxError.BAD_FIELD, 'mountOptions must be an object');
+
     const error = mounts.validateMountOptions(storageConfig.provider, storageConfig.mountOptions);
     if (error) throw error;