Remove dead ArrayData::nvGet() functions.

They were dead.

hphp/runtime/base/array/array_data.cpp

@@ -486,19 +486,6 @@ CVarRef ArrayData::get(CVarRef k, bool error) const {
                         : get(getStringKey(cell), error);
 }
 
-// nvGet has to search twice when using the ArrayData api so as not to
-// conflate no-key with have-key && value == null_varaint.  Subclasses
-// can easily do this with one key search.
-
-TypedValue* ArrayData::nvGet(int64_t k) const {
-  return exists(k) ? (TypedValue*)&get(k, false) :
-         nullptr;
-}
-
-TypedValue* ArrayData::nvGet(const StringData* key) const {
-  return exists(key) ? (TypedValue*)&get(key, false) : nullptr;
-}
-
 void ArrayData::nvGetKey(TypedValue* out, ssize_t pos) {
   Variant k = getKey(pos);
   TypedValue* tv = k.asTypedValue();

hphp/runtime/base/array/array_data.h

@@ -214,8 +214,8 @@ public:
    * Interface for VM helpers.  ArrayData implements generic versions
    * using the other ArrayData api; subclasses may do better.
    */
-  virtual TypedValue* nvGet(int64_t k) const;
-  virtual TypedValue* nvGet(const StringData* k) const;
+  virtual TypedValue* nvGet(int64_t k) const = 0;
+  virtual TypedValue* nvGet(const StringData* k) const = 0;
   virtual void nvGetKey(TypedValue* out, ssize_t pos);
   virtual TypedValue* nvGetValueRef(ssize_t pos);
   virtual TypedValue* nvGetCell(int64_t ki) const;