[turbofan] Make FindFrameStateBefore handle dead paths.

src/compiler/node-properties.cc

Index: src/compiler/node-properties.cc
diff --git a/src/compiler/node-properties.cc b/src/compiler/node-properties.cc
index 23dfcda0cbac8150965b9c2209b39f462b3236ef..9451df8566dadbb952d43aa88e36171155e896ad 100644
--- a/src/compiler/node-properties.cc
+++ b/src/compiler/node-properties.cc
@@ -239,6 +239,7 @@ void NodeProperties::ChangeOp(Node* node, const Operator* new_op) {
 Node* NodeProperties::FindFrameStateBefore(Node* node) {
   Node* effect = NodeProperties::GetEffectInput(node);
   while (effect->opcode() != IrOpcode::kCheckpoint) {
+    if (effect->opcode() == IrOpcode::kDead) return effect;
     DCHECK_EQ(1, effect->op()->EffectInputCount());
     effect = NodeProperties::GetEffectInput(effect);
   }