Unhandled error in observer: object 'input' not found

Question

I am trying to make a R shiny APP that runs an executable program. I am new to shiny so sorry if this question should be obvious but I have looked and can't find anything that addresses my problem. Everything runs fine until the call to function runhysplit(). My question is: why do I get the following error when running the code below:

"Warning: Unhandled error in observer: object 'input' not found observeEvent(input$runHys)."

    library(opentraj)
    library(plyr)
    library(shiny)
    library(shinydashboard)
    source('/root/Desktop/HysplitMatcher/runhysplit.R')
    ui <- {dashboardPage(
    dashboardHeader(title = "HYSPLIT TRAJECTORY MATCHING TOOL", titleWidth=450),
    dashboardSidebar(
                  sidebarMenu(
                              menuItem("Multiple Trajectories", tabName =   "dashboard", icon = icon("dashboard")),
                              menuItem("Widgets", tabName = "widgets", icon   = icon("th"))

                    )

    ), 
  dashboardBody(

              numericInput(inputId="hour.interval", label = "Hour Interval", value = 1),
              numericInput(inputId="hours", label = "Total Run Time (hours)", value = -72), 
              selectInput(inputId ="metdata", label="Meteorology Data:", choices=c("North American Model (NAM) 00Z", "North American Model (NAM) 12Z"), selected = NULL, width = NULL),
              selectInput(inputId ="location", label="Location", choices=c("Evansville", "Indianapolis Metro", "Gary", "Standiford Field (Louisville)", "South Bend")),
              numericInput(inputId="height", label="Height AGL", value=100),
              dateRangeInput(inputId="dates", label="Enter a date range (yyyy-mm-dd)", format="yyyy-mm-dd", separator = " to "),
              numericInput(inputId="start.hour", label="Enter a staring time (hh:mm)", value = ""),
              numericInput(inputId ="end.hour", label="Enter an ending time (hh:mm)", value = ""),
                      actionButton(inputId ="runHys", label ="RunHysplit"),
                      textOutput("dates")
  #                  submitButton("Get Trajectories")
              )
        )
    }


    server <- function(input, output) {

    results <- observeEvent(input$runHys, {
    lat <- c(37.9772, 39.7910, 41.5956, 38.1742, 41.6725)  
    lon <- c(-87.5506, -86.1480, -87.3453, -85.7364, -86.2553)
    locations <- c("Evansville", "Indianapolis Metro", "Gary", "Standiford             Field (Louisville)", "South Bend")
    latlonlook <- data.frame(lat,lon,locations)
    latlonlook <- subset(latlonlook, locations == input$location)
    lat <- latlonlook$lat
    lon <- latlonlook$lon
    cat(lat)
    cat("\n")
    cat(lon)
    dateseq <- seq(from=input$dates[1], to=input$dates[2], by=1)
    cat("\n")
    cat(dateseq)
    cat("\n")
    cat(input$hour.interval)
    cat("\n")
    cat(input$metdata)
 runhysplit(lat=lat, lon=lon, hour.interval=input$hour.interval, name="hysplit_fore",start.hour=input$start.hour, end.hour=input$end.hour, met="/root/Desktop/HysplitMatcher/",out="/root/Desktop/HysplitMatcher/", hours=input$hours, height=input$height, hy.path="/root/hysplit/trunk/", ID=1, dates=dateseq, metdata=input$metdata) 
})
}

shinyApp(ui, server)