SetExprFields fails when run from the command line

Summary

There is a typo on line 774 of setExprFields.C that causes the tool to fail when specifying an expression via the command line rather than a dict.

Steps to reproduce

It occurs for any scenario where the command line interface is used

Example case

What is the current bug behaviour?

the command fails with an out of range error.

What is the expected correct behavior?

The setExpField command should run correctly and set/create the field.

Relevant logs and/or images

Environment information

• OpenFOAM version : v2012
• Operating system : ubuntu
• Hardware info :
• Compiler : gcc

Possible fixes

change line 774 of setExprFields.C from args[expression], to args["expression"],