Unfortunetly,the process com.android.systemui has stopped. samsung galaxy grand 2

A

AC Question

i am having samsung galaxy grand 2 handset. when i am holding the bottom home key to clean background running apps its showing me- Unfortunetly,the process com.android.systemui has stopped. and as i cliked ok botton my mobile screen get locked and i have to again unlock it. not able to clean backgroung running apps. please help me by giving some solution.