Null values creating new errors in edit query conditionals

Hi all,

I have an employee data report where I have added a number of conditional statements to determine things like which employees were hired in specific timeframes, termed in specific timeframes, etc. I haven't changed anything in the source files or the report, but between last week's report run and this week's, all of my conditional query strings are giving off errors anytime there is a null value.  Previously, the "else" final default command addressed these, but I have no idea why these are throwing off error codes now.

Is there a setting in PowerBI to change the functionality and allow the final "else" clause to include nulls and just return a zero or null as I have done in the past?  I implemented a workaround here to add steps to replace all errors with "null," but something changed for me this past week and I would really like to figure it out!  

Here is an example of the conditional I have always been sucessful with in the past.  (you can skip the comments about how I should be writing measures instead, I learned PowerBI via YouTube videos and haven't progressed that far yet :))

And here is a screenshot of the errors I am getting for the first time... all of them appear to relate to when the conditional is referencing a null value.  Again, no changes in anything, but previously, these just returned the zero or null I wanted.  Now, throwing off errors.

One workaround seemed to be adding a conditional line to address the null values, but then I figured it was easier to just replace the errors with zeros.