Fuzz bug with DCE on pop moved into block in old EH

[kripken]

(module
 (type $struct (struct (field (mut (ref null eq)))))

 (tag $tag (param (ref null eq)))

 (func $0 (result i32)
  (try (result i32)
   (do
    (i32.const 0)
   )
   (catch $tag
    (drop
     (ref.eq
      (struct.new $struct
       (pop (ref null eq))
      )
      (unreachable)
     )
    )
    (i32.const 0)
   )
   (catch_all
    (i32.const 0)
   )
  )
 )
)

$ bin/wasm-opt a.wat -all --dce 
[wasm-validator error in function 0] unexpected false: , on 
(try (result i32)
 (do
  (i32.const 0)
 )
 (catch $tag
  (block
   (drop
    (struct.new $struct
     (pop eqref)
    )
   )
   (unreachable)
  )
 )
 (catch_all
  (i32.const 0)
 )
)
catch's body (tag)'s pop's location is not validFatal: error after opts

cc @aheejin