title: Android sometimes force kills application
body: <p>I start activity A, then start activity B.<br>
  I press home button, then waiting long time.<br>
  When I resume application, it force stopped.  </p>
  
  <pre><code>02-03 18:42:54.413 828-844/system_process I/ActivityManager: Force stopping ru.tabor.search appid=10089 user=0: from pid 20405
  02-03 18:42:54.414 828-844/system_process I/ActivityManager: Killing 30212:ru.tabor.search/u0a89 (adj 7): stop ru.tabor.search
  02-03 18:42:54.445 828-5948/system_process I/WindowState: WIN DEATH: Window{18b92c9b u0 ru.tabor.search/ru.tabor.search.modules.authorization.AuthorizationActivity}
  02-03 18:42:54.447 828-845/system_process I/WindowState: WIN DEATH: Window{1cd0cfe4 u0 ru.tabor.search/ru.tabor.search.modules.registration.RegistrationActivity}
  02-03 18:42:54.519 828-844/system_process I/ActivityManager:   Force finishing activity 3 ActivityRecord{25a8977f u0 ru.tabor.search/.modules.authorization.AuthorizationActivity t2593}
  02-03 18:42:54.520 828-844/system_process I/ActivityManager:   Force finishing activity 3 ActivityRecord{d516838 u0 ru.tabor.search/.modules.registration.RegistrationActivity t2593}
  02-03 18:42:54.523 828-20666/system_process W/ActivityManager: Spurious death for ProcessRecord{21ff313b 0:ru.tabor.search/u0a89}, curProc for 30212: null
  02-03 18:42:59.890 828-1247/system_process I/ActivityManager: START u0 {act=android.intent.action.MAIN cat=[android.intent.category.LAUNCHER] flg=0x10100000 cmp=ru.tabor.search/.modules.authorization.AuthorizationActivity} from uid 10089 on display 0
  02-03 18:42:59.903 828-1247/system_process V/WindowManager: addAppToken: AppWindowToken{1c4987a0 token=Token{279a08a3 ActivityRecord{9f5afd2 u0 ru.tabor.search/.modules.authorization.AuthorizationActivity t2593}}} to stack=1 task=2593 at 0
  02-03 18:42:59.919 828-891/system_process V/WindowManager: Adding window Window{1735e91b u0 Starting ru.tabor.search} at 4 of 8 (after Window{2ab6bf53 u0 com.cleanmaster.mguard/com.keniu.security.main.MainActivity})
  02-03 18:43:19.288 828-1673/system_process I/ActivityManager: Start proc 21366:ru.tabor.search/u0a89 for activity ru.tabor.search/.modules.authorization.AuthorizationActivity
  </code></pre>
  
  <p>How to fix it?</p>