more google merge fixes

include/flatbuffers/flatbuffer_builder.h

@@ -739,7 +739,7 @@ class FlatBufferBuilder {
   /// @return Returns a typed `Offset` into the serialized data indicating
   /// where the vector is stored.
   template<typename StringType = std::string,
-           typename Alloc = std::allocator<std::string>>
+           typename Alloc = std::allocator<StringType>>
   Offset<Vector<Offset<String>>> CreateVectorOfStrings(
       const std::vector<StringType, Alloc> &v) {
     return CreateVectorOfStrings(v.cbegin(), v.cend());

include/flatbuffers/vector.h

@@ -19,6 +19,7 @@
 
 #include "flatbuffers/base.h"
 #include "flatbuffers/buffer.h"
+#include "flatbuffers/stl_emulation.h"
 
 namespace flatbuffers {
 

src/idl_gen_cpp.cpp

@@ -3267,7 +3267,8 @@ class CppGenerator : public BaseGenerator {
         // If set_empty_vectors_to_null option is enabled, for optional fields,
         // check to see if there actually is any data in _o->field before
         // attempting to access it.
-        if (opts_.set_empty_vectors_to_null && !field.IsRequired()) {
+        if (field.attributes.Lookup("nested_flatbuffer") ||
+            (opts_.set_empty_vectors_to_null && !field.IsRequired())) {
           code = value + ".size() ? " + code + " : 0";
         }
         break;