QGIS - Model builder flexibility and errors

I'm trying to build a simple multi-step selection (by attribute) with the model builder. I created a simple sample layer to avoid data-driven errors. Now I want to query the layer and select features 1) by feature attribute "name" AND/OR 2) by feature attribute "age". The model executes the first query (name), picking up two features and then fails on the second, which should result in the selection of a single feature.

The log tells me "Error executing algorithm 1 local variable 'x' referenced before assignment See log for more details". The "History and log" (under Processing) ERROR section tells me to "See log for more details". So two logs tell me to look at a log. Is there a third log somewhere?

Another problem is that the selection comparison only allows one option (e.g. "=="). This is problematic because I want to be able to search for just "age" as well. Leaving the field for name blank selects nothing.

A few screenshots:

Using the build has also been a quite frustrating experience so far. Python errors our of the blue, not being able to delete algorithms before filling the input variable fields with garbage, nor being able to delete algorithms at all and QGIS just crashing. Is this "normal"?