changes to bruker.py according to PR comments * check proc_files against None * check for the existence of files passed to bin_files
changes to bruker.py according to PR comments
* check proc_files against None
* check for the existence of files passed to bin_files

kaustubhmote/nmrglue,kaustubhmote/nmrglue,jjhelmus/nmrglue,jjhelmus/nmrglue