ProcessStats: Fix another crasher

Prevent occurences of:

java.util.NoSuchElementException
	at java.util.StringTokenizer.nextToken(StringTokenizer.java:208)
	at com.android.internal.os.ProcessStats.getCpuSpeedTimes(ProcessStats.java:574)
	at com.android.internal.os.ProcessStats.getLastCpuSpeedTimes(ProcessStats.java:546)
	at com.android.server.am.ActivityManagerService.updateCpuStatsNow(ActivityManagerService.java:1676)
	at com.android.server.am.ActivityManagerService.batteryNeedsCpuUpdate(ActivityManagerService.java:1728)
	at com.android.internal.os.BatteryStatsImpl$MyHandler.handleMessage(BatteryStatsImpl.java:129)
	at android.os.Handler.dispatchMessage(Handler.java:99)
	at android.os.Looper.loop(Looper.java:137)
	at com.android.server.am.ActivityManagerService$AThread.run(ActivityManagerService.java:1431)

Change-Id: I66f30739455dd726b708467f814f53c445f327b2