Return `exit-code` when `reporter` is invalid

[nulls]

Now we get

<reporter> should be set to <sarif> or <checkstyle>
Error: Process completed with exit code 1.
Run if ((  == 0 ))
/home/runner/work/_temp/d4e0e34c-bf86-4484-a6e8-9993c[67](https://github.com/nulls/diktat/pull/3/checks#step:3:70)45502.sh: line 1: ((: == 0 : syntax error: operand expected (error token is "== 0 ")
/home/runner/work/_temp/d4e0e34c-bf86-4484-a6e8-9993c6745502.sh: line 14: ((: != 0 : syntax error: operand expected (error token is "!= 0 ")
/home/runner/work/_temp/d4e0e34c-bf86-4484-a6e8-9993c6745502.sh: line 21: ((: <= 1 : syntax error: operand expected (error token is "<= 1 ")
/home/runner/work/_temp/d4e0e34c-bf86-4484-a6e8-9993c6745502.sh: line 26: ((: != 1 : syntax error: operand expected (error token is "!= 1 ")
Error: Process completed with exit code 1.