Unable to update and save merchant details for a merchant with Facebook

Steps:
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1. Login to Reseller UI.
2. Create a merchant with Facebook checkbox enabled.
3. Enter all the values of a merchant.
4. Save the merchant.
5. Update the merchant name or contact firstname or contact lastname etc,.
6. Save the merchant.

Actual: Merchant details was not saved and we are getting an Error popup in Reseller UI. See the attached screenshot.

Expected: Merchant should save successfully with updated merchant details.

Note: This is happening only when we create merchant with External API.

See the attached tomcat log.