fmt::ostream move constructor does not properly initialize buffer

[Boostibot]

The following code causes a segmentation fault:

fmt::ostream temp_file = fmt::output_file("file.txt");
fmt::ostream move_constructed(std::move(temp_file));
move_constructed.print("Hello world"); //SIGSEGV - Segmentation fault

This is because the internal buffer pointer and data is left uninitialised and left pointing to null.

The following change to fmt::ostream::ostream(ostream&& ) solves this issue

ostream(ostream&& other) : file_(std::move(other.file_)) {
    set(other.data(), other.capacity()); //Added - Initialises the data
    other.set(nullptr, 0);
  }

[vitaut]

Could you submit a PR?

[vitaut]

Fixed in 6cccdc2. Thanks for catching this.