Add catch exception incase of PHP errors

[bismitaguha]

Signed-off-by: Bismita Guha bguha@mt.iitr.ac.in

Description

Added try-catch to MonitorController.php to display warnings.

Fixes #15897

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[williamdes]

@bismitaguha what are the warnings?
Can you say what throws the warnings in the code?

[bismitaguha]

@williamdes Any kind of PHP error is caught and the warning displayed is the $err->message of the Exception caught.

[williamdes]

I do not agree with this change because it is a hack that will not fix all possible issues.
User must have iconv extension.