Unused variable in the Kernel

Stream: lean4

[Henrik Böving]

While compiling Lean I noticed a warning about an unused variable, namely this one: https://github.com/leanprover/lean4/blob/master/src/kernel/inductive.cpp#L617 it does get initialized and a little further down it does get incremented as well but never used. Is this potentially a bug from some refactoring in the past that was overseen?