Fix a bootloop problem when /data/system/usagestats/usage-history.xml is an empty file.
See : http://blog.csdn.net/fgwf1/article/details/10624887

Change-Id: I4f01151f4051df4ae1b85fa460ec7a9e70122878
Merge "Fix a bootloop problem when /data/system/usagestats/usage-history.xml is an empty file. See : http://blog.csdn.net/fgwf1/article/details/10624887" into kk_mkt