Ensure concrete re-executions are resilient to behavior variation

[pschanely]

Context: To avoid false-positives from approximations like real-based floats, we don't actually report the error right away; instead we'll abort the failing pass and try to recreate the pass next time with concrete draws. This can go haywire though if the requested draw types aren't the same on the next pass.

But it really shouldn't go fully haywire. From this discussion:

I should change the provider to ensure it yields SOME value of the requested type.
After all, I'm running the concrete execution under the premise that the behavior
might actually differ, so I shouldn't be quite so surprised when it does. 😆

[pschanely]

Fixed in de46347 (but not yet deployed)