rb_thrift_memory_buffer_write treats arg as string without check, segfaults if you pass non-string

I think there should be a call to Check_Type(str, T_STRING) in there

VALUE rb_thrift_memory_buffer_write(VALUE self, VALUE str) {
VALUE buf = GET_BUF(self);
rb_str_buf_cat(buf, RSTRING_PTR(str), RSTRING_LEN(str));
return Qnil;
}