optimizer: handle EnterNode with catch_dest == 0 (#56686)

In some parts of the optimizer code, such as `cfg_simplify!` and
irinterp, it is assumed that `EnterNode` always has `catch_dest ≠ 0`,
but this assumption is incorrect. This commit fixes those cases.

Compiler/src/ssair/irinterp.jl

@@ -249,8 +249,10 @@ function process_terminator!(@nospecialize(stmt), bb::Int, bb_ip::BitSetBoundedM
         return backedge
     elseif isa(stmt, EnterNode)
         dest = stmt.catch_dest
-        @assert dest > bb
-        push!(bb_ip, dest)
+        if dest ≠ 0
+            @assert dest > bb
+            push!(bb_ip, dest)
+        end
         push!(bb_ip, bb+1)
         return false
     else

Compiler/src/ssair/passes.jl

@@ -2393,8 +2393,10 @@ function cfg_simplify!(ir::IRCode)
                     end
                 elseif isa(terminator, EnterNode)
                     catchbb = terminator.catch_dest
-                    if bb_rename_succ[catchbb] == 0
-                        push!(worklist, catchbb)
+                    if catchbb ≠ 0
+                        if bb_rename_succ[catchbb] == 0
+                            push!(worklist, catchbb)
+                        end
                     end
                 elseif isa(terminator, GotoNode) || isa(terminator, ReturnNode)
                     # No implicit fall through. Schedule from work list.

Compiler/test/irpasses.jl

@@ -1816,7 +1816,34 @@ function f53521()
         end
     end
 end
-@test code_typed(f53521)[1][2] === Nothing
+let (ir,rt) = only(Base.code_ircode(f53521, ()))
+    @test rt == Nothing
+    Compiler.verify_ir(ir)
+    Compiler.cfg_simplify!(ir)
+    Compiler.verify_ir(ir)
+end
+
+Base.@assume_effects :foldable Base.@constprop :aggressive function f53521(x::Int, ::Int)
+    VALUE = ScopedValue(x)
+    @with VALUE => 2 begin
+        for i = 1
+            @with VALUE => 3 begin
+                local v
+                try
+                    v = sin(VALUE[])
+                catch
+                    v = nothing
+                end
+                return v
+            end
+        end
+    end
+end
+let (ir,rt) = only(Base.code_ircode((Int,)) do y
+        f53521(1, y)
+    end)
+    @test rt == Union{Nothing,Float64}
+end
 
 # Test that adce_pass! sets Refined on PhiNode values
 let code = Any[