Update server.R

do not need the last if statement and because there is no other else statement, it will pop up warning message. Thus I just change it to comment (line 123) to avoid affect running.
"Warning in grep(input$net.eff, tmp) :
  argument 'pattern' has length > 1 and only the first element will be used
Warning in grep(input$net.ele, tmp) :
  argument 'pattern' has length > 1 and only the first element will be used"