fix: only use OffsetArray if starting index is not 1

Author: AayushSabharwal

src/structural_transformation/symbolics_tearing.jl

@@ -592,7 +592,9 @@ function tearing_reassemble(state::TearingState, var_eq_matching,
 
         # respect non-1-indexed arrays
         # TODO: get rid of this hack together with the above hack, then remove OffsetArrays dependency
-        obs_arr_subs[arg1] = Origin(index_first)(obs_arr_subs[arg1])
+        if !isone(index_first)
+            obs_arr_subs[arg1] = Origin(index_first)(obs_arr_subs[arg1])
+        end
     end
     for i in eachindex(neweqs)
         neweqs[i] = fast_substitute(neweqs[i], obs_arr_subs; operator = Symbolics.Operator)