[backport-v9] fix: fix infinite recursion in `full_equations`#3672

ChrisRackauckas merged 1 commit intoSciML:backport-v9SciML/ModelingToolkit.jl:backport-v9from

AayushSabharwal:as/infinite-recursionAayushSabharwal/ModelingToolkit.jl:as/infinite-recursionCopy head branch name to clipboard