[turbofan] Fix merging of empty and non-empty state in load elimination.

src/compiler/load-elimination.cc

Index: src/compiler/load-elimination.cc
diff --git a/src/compiler/load-elimination.cc b/src/compiler/load-elimination.cc
index ad787f80928be553075a3e130fd534b9fc478eaa..6131fc57d4ec333ef6eac76a01640aac21607d53 100644
--- a/src/compiler/load-elimination.cc
+++ b/src/compiler/load-elimination.cc
@@ -219,9 +219,7 @@ void LoadElimination::AbstractState::Merge(AbstractState const* that,
   if (this->elements_) {
     this->elements_ = that->elements_
                           ? that->elements_->Merge(this->elements_, zone)
-                          : that->elements_;
-  } else {
-    this->elements_ = that->elements_;
+                          : nullptr;
   }
 
   // Merge the information we have about the fields.