Update src/systems/alias_elimination.jl

Co-authored-by: Aayush Sabharwal <aayush.sabharwal@gmail.com>

Author: oscardssmith

src/systems/alias_elimination.jl

@@ -346,7 +346,8 @@ function find_perfect_aliases!(
         # (`v - target` with `v→target` leaves neither). Substitution never
         # introduces new vars, so the new incidence is a subset of the old —
         # prune the row to entries actually present in the simplified RHS.
-        new_vars = Symbolics.get_variables(eqs[e], fullvars)
+        empty!(new_vars)
+        SU.search_variables!(new_vars, eqs[e])
         new_row = filter(v_idx -> fullvars[v_idx] in new_vars, 𝑠neighbors(graph, e))
         BipartiteGraphs.set_neighbors!(graph, e, new_row)
     end