Segmentation Fault(core dumped) C++11 Tree class

I'm coding a bk-tree to use in my criptography work, but I'm having a segmentation fault(core dumped) with a simply setString method I created, I researched about what my error could be but unfortunately I couldn't find an answer.

I don't know if my code is working since I can't even test the insertions, here is the code(I had to put every file in this link since I don't have enough reputation to post more than 2 links and if I pasted everything here, would turn into a mess, sorry) Code: http://ift.tt/1HqKWy0

Thank you