[Tooling] Syntax error shown while templating variables

[pcnfernando]

Description:
When we try to template some specific operators, tooling shows an syntax error even when a value is set for the templated variables.
My guess is this because of the frontend syntax validations we run within the ACE editor.

Steps to reproduce:
Template the length size of a length batch window.
Populate the set variable.

When this Siddhi application is deployed in runner with the environment variables set correctly, it runs as expected.

[suhothayan]

Fixed in Siddhi 5.1.2 release