Random text view

I`m have a problem because when i touch my button sometimes not appear my text... (Sorry for my English!) code: function randomText(event)

display.remove(mmDis)

local a = {"Cristiano ronaldo jest najlepszy!", "messi jest dobry!","lewandowski jest ok","diego lopez to bramkarz realu"}

com = (a[math.random(1,#a)])


local mmDis = display.newText(tostring(com), 
    display.contentWidth*0.57, display.contentHeight*0.7,               
    display.contentWidth*0.9, display.contentHeight*0.8, "Impact", 30)
    mmDis.y=20
    mmDis.x=190
    mmDis:setFillColor(0, 0, 0, 1)  
    mmDis.anchorY = 0    

end

play:addEventListener ("tap", randomText )

Help please !!!