Question [Q] "null?" file in phone internall memory

Today I decided to clean up the memory on my Trend Plus, because I had only half a giga free. I deleted some junk files from old games that I had that were about another half a giga in size. But I also found a file named "null?" inside a folder inside the Android folder (where the ap data and game obbs are). So I deleted it, and suddenly I got another half a giga free! After I rebooted my phone, all the apps where still there, and worked properly, but the extra storage remained. So now, I have 1,5 giga free. What was that "null?" file? I found it via the Drive Storage Analyser app, but the 1,5 giga was confirmed through the phone settings. Could they be important files that will come up later?