help for this problem

extrafiles1=$(ls mt.*.*.*.*) 
extrafiles2=$(ls *core*) 

my question is--
suppose if there is no files matching with the criteria mentioned above it will display message on the window--
mt.*.*.*.* not found
*core* not found

i do not want to display this message on the window even if it do not find any files matching with the criteria,how can i do that.

extrafiles1=$(ls mt.*.*.*.* 2>/dev/null) 
extrafiles2=$(ls *core* 2>/dev/null)