Warning: Error in if: argument is of length zero

the code works perfectly until I select radio buttons (to filter the data by different values, be it by country/office/customer/etc..) i get this error:

Warning: Error in if: argument is of length zero
  125: <reactive:officedata> [C:\Users\jzuraik\Desktop\shiny-Dashboard/server.R#247]
  109: officedata
   97: vbox_fun [C:\Users\jzuraik\Desktop\shiny-Dashboard/server.R#328]
   96: shiny::renderUI
   95: func
   82: origRenderFunc
   81: output$numofenqby
    1: runApp
Warning: Error in if: argument is of length zero
  130: <Anonymous>
Warning: Error in if: argument is of length zero
  112: <Anonymous>
Warning: Error in if: argument is of length zero
  130: <Anonymous>
Warning: Error in if: argument is of length zero
  111: <Anonymous>
Warning: Error in if: argument is of length zero
  118: <Anonymous>
Warning: Error in if: argument is of length zero
  129: <Anonymous>
Warning: Error in if: argument is of length zero
  101: <Anonymous>
Warning: Error in if: argument is of length zero
  101: <Anonymous>

and here are the mentioned lines of code that contains this error:

officedata <- reactive({

   #office country Radio Button id selescted
   if(input$analysisLevel == 1)
   {
   subset(
     ct,
   ct$`Office Country` %in%  input$officecountry
   )
   }
   # office Radio Button id selescted
   else if(input$analysisLevel == 2)
     {
       subset(
         ct,
         ct$Office %in%  input$office
       )
     }
     else if(input$analysisLevel == 3)
       {
     subset(
       ct,
       ct$Market %in%  input$market
     )
     }
   else if(input$analysisLevel == 4)
   {
     subset(
       ct,
       ct$`Source Market` %in%  input$sourcemarket
     )
   }
   else if(input$analysisLevel == 5)
   {
     subset(
       ct,
       ct$Customer %in%  input$customer
     )
   }
   else{
     return(ct)
   }
 })

 #filtered data
 filteredcancelled <- reactive({
   subset(
     officedata(),
     officedata()$Status %in% "Cancelled"
   )
 })

 #Average Project Size
 officedataconcom <- reactive({ 
   subset(
     officedata(),
     officedata()$Start >= "2018-01-01" &
       officedata()$Status == "Completed" |
       officedata()$Status == "Confirmed"
   )
 })

 #pendreq
 pendreqfilter <- reactive({
   subset(
     officedata(),
     officedata()$Start >= "2018-01-01" &
       officedata()$Status %in% "Request"
   ) 
 })

 #past req

 pastrequestsdatefilter <- reactive({
   subset(
     pendreqfilter(),
     pendreqfilter()$Start< Sys.Date() 

   )
 })


 ##############################DATA BY OFFICE OFFICE COUNTRY MARKET SOURCE MARKET AND CUSTOMER###########################
 output$numofenqby <- renderValueBox({
   valueBox(nrow(officedata()), "Number of Enquiries", color = "blue", icon = icon("star"))

 })

i reviewed them to try to catch what is the error, but I couldn't, and I also tried to review similar questions in stackoverflow before posting this question, but with no vain.

and a very important thing is that my code still works, even with this warning. it is just a warning, but i prefer to get rid of it.

this is the output that when i click different options it gives me the mentioned above errors: so my console stays clean until i try to shuffle between those different buttons (Office Country/Office/Market/Source Market/Customer), and when i do, I get those Warning..

Any help please? I would be really thankful