Problem with if-then-else in determinate when the then branch is not accessible

[VincentCheval]

In determinate process, there is an optimisation that does not generate constraint systems for else-branch when all the else branches are 0. However it is problematic when the then branch is not accessible as it would generate an error if matched with a process that does not have an if-then-else test.

ifthenelse_determinate.txt