Standardize a method to gracefully handle missing files

[WildWeazel]

This is more of an epic, and surely will be a recurring theme throughout the project...

Given how data-driven and customizable this game is intended to be, we can expect that files will sometimes be missing, even if they're part of our own distribution. For example I ran into an issue when switching branches where some fonts or at least their import files were missing, and this brought down half of the render loop. Whenever we read a file we should assume that it may fail, and try to deal with it. Depending on the file, this may include any combination of:

• explicitly check the result before continuing
• use the null conditional operator ?. to access it
• LOG IT at a high level (this should eventually be shown in-game)
• default to a placeholder/empty reference at the lowest level possible
• disable the feature
• if it's absolutely critical, abort back to the nearest safe state