UpdateConfigHdr: Gracefully exit when filepath is `None`

[Javagedes]

Description

GetAbsolutePathOnThisSystemFromEdk2RelativePath will log an error message and return None if absolute path could not be determined. Due to this, file should be checked against None, not os.path.isfile.

You can see that in the GetAbsolutePathOnThisSystemFromEdk2RelativePath that we return a str if the absolute path is found, else None.

Currently, when a path is not found, you get this exception and trace:

• [ ] Impacts functionality?
  • Functionality - Does the change ultimately impact how firmware functions?
  • Examples: Add a new library, publish a new PPI, update an algorithm, ...
• [ ] Impacts security?
  • Security - Does the change have a direct security impact on an application, flow, or firmware?
  • Examples: Crypto algorithm change, buffer overflow fix, parameter validation improvement, ...
• [ ] Breaking change?
  • Breaking change - Will anyone consuming this change experience a break in build or boot behavior?
  • Examples: Add a new library class, move a module to a different repo, call a function in a new library class in a pre-existing module, ...
• [ ] Includes tests?
  • Tests - Does the change include any explicit test code?
  • Examples: Unit tests, integration tests, robot tests, ...
• [ ] Includes documentation?
  • Documentation - Does the change contain explicit documentation additions outside direct code modifications (and comments)?
  • Examples: Update readme file, add feature readme file, link to documentation on an a separate Web page, ...

How This Was Tested

N/A

Integration Instructions

N/A