Fix an issue in the WebSocket data provider

[lasanthaS]

Purpose

This PR fixes an issue in the WebSocket data provider while creating a widget via the Widget generation wizard.

Security checks

• Followed secure coding standards in http://wso2.com/technical-reports/wso2-secure-engineering-guidelines? yes
• Ran FindSecurityBugs plugin and verified report? yes
• Confirmed that this PR doesn't commit any keys, passwords, tokens, usernames, or other secrets? yes