fix compute_trycatch for IRCode /w EnterNode with catch_dest==0 (#56846)

Author: aviatesk

Compiler/src/inferencestate.jl

@@ -475,7 +475,7 @@ function (::ComputeTryCatch{Handler})(code::Vector{Any}, bbs::Union{Vector{Basic
             (;handlers, handler_at) = handler_info =
                 (handler_info === nothing ? HandlerInfo{Handler}(Handler[], fill((0, 0), n)) : handler_info)
             l = stmt.catch_dest
-            (bbs !== nothing) && (l = first(bbs[l].stmts))
+            (bbs !== nothing) && (l != 0) && (l = first(bbs[l].stmts))
             push!(handlers, Handler(stmt, pc))
             handler_id = length(handlers)
             handler_at[pc + 1] = (handler_id, 0)
@@ -519,7 +519,7 @@ function (::ComputeTryCatch{Handler})(code::Vector{Any}, bbs::Union{Vector{Basic
                 break
             elseif isa(stmt, EnterNode)
                 l = stmt.catch_dest
-                (bbs !== nothing) && (l = first(bbs[l].stmts))
+                (bbs !== nothing) && (l != 0) && (l = first(bbs[l].stmts))
                 # We assigned a handler number above. Here we just merge that
                 # with out current handler information.
                 if l != 0

Compiler/test/irpasses.jl

@@ -1716,6 +1716,12 @@ end
 @test scope_folding_opt() == 1
 @test_broken fully_eliminated(scope_folding)
 @test_broken fully_eliminated(scope_folding_opt)
+let ir = first(only(Base.code_ircode(scope_folding, ())))
+    @test Compiler.compute_trycatch(ir) isa Compiler.HandlerInfo
+end
+let ir = first(only(Base.code_ircode(scope_folding_opt, ())))
+    @test Compiler.compute_trycatch(ir) isa Compiler.HandlerInfo
+end
 
 # Function that happened to have lots of sroa that
 # happened to trigger a bad case in the renamer. We