The regression was introduced to align 3DS export and import, but in fact it broke the transformation matrices on import. This commit reverts the relevant lines. Furthermore, matrix layout was double-checked with two other 3DS importers. Export was not considered.
std::string s(""); s = ""; calls the copy constructor, which in turn calls strlen(), … assigning a default-constructed string generates fewer instructions and is therefore preferred.
With C++11 uniform initialization, you’d simply write s = { } instead.