Task: find all runtimeError-capable lines and make sure they are guarded

[tlambert03]

It would be a handy thing to know, a priori, what calls to mmcore are likely to cause RuntimeErrors (or other errors) in a config-dependent way. And make sure that we're catching and handling them appropriately throughout the widgets here.

A manual approach might be looking through the CMMCore code and seeing what throws. or an automated approach could to load either no config or the demo config, and just try calling all of the methods with type-appropriate values... Some will just return sane defaults (like getPixelSizeUm) while others will raise exceptions.

Then, we can look through the code here and make sure we have appropriate error handling logic in place.

[tlambert03]

see, for example, pymmcore-plus/napari-micromanager#288 ... where each problem fixed gradually reveals a new problem on a new, untested config