Add ROOT File close()
Created by: gpronost
I noticed in some rare cases, the Neighbouring PMT file is corrupted (ROOT complained about it not being correctly closed). The reason is not clear: It may be due to a crash of the program, to FLOWER not being correctly deleted in some occasions, or to the fact this root files is opened simultaneously by several different instance of FLOWER.
Adding f.Close() after reading/writing the neighbouring PMTs seems to help the resolution of this issue.