Error message for null pointer issues can be improved

[sachinmaheshwari]

Issue Template

Context

Currently, if there is any null pointer related issue in the rule, we are dumping an error message which is not really informative. For e.g.

java.lang.RuntimeException: Invalid function name or incorrect number of arguments passed: res['ownerId'].equals(sub['firstName'].toLowerCase().concat('.').concat(sub['lastName'].toLowerCase()))

whereas, the actual error was:

Attempted to call method toLowerCase() on null context object

Expected Behavior

The error message should be informative and point to the actual issue.

[rohit256]

Is this available for hacktober fest ? If yes, could you assign this to me ?