Fix IfBuilder::Deopt to clear the current block.

src/hydrogen.cc

Index: src/hydrogen.cc
diff --git a/src/hydrogen.cc b/src/hydrogen.cc
index 1df062c9ee0abf73fec7b30b831c4ffa12f8f6ef..eef1d6b23b99189a17bed57d7266cb31a8e2c1b7 100644
--- a/src/hydrogen.cc
+++ b/src/hydrogen.cc
@@ -812,6 +812,7 @@ void HGraphBuilder::IfBuilder::Else() {
 void HGraphBuilder::IfBuilder::Deopt() {
   HBasicBlock* block = builder_->current_block();
   block->FinishExitWithDeoptimization(HDeoptimize::kUseAll);
+  builder_->set_current_block(NULL);
   if (did_else_) {
     first_false_block_ = NULL;
   } else {
@@ -7194,6 +7195,7 @@ HValue* HOptimizedGraphBuilder::HandlePolymorphicElementAccess(
 
   // If only one map is left after transitioning, handle this case
   // monomorphically.
+  ASSERT(num_untransitionable_maps >= 1);
   if (num_untransitionable_maps == 1) {
     HInstruction* instr = NULL;
     if (untransitionable_map->has_slow_elements_kind()) {