Shiny/R call reactive function

Can anybody hel me with Shiny framework / R language? I have

Warning: Error in <-: object of type 'symbol' is not subsettable 
Stack trace (innermost first): 
113: lm.regsubsets3 [C:\R\Application/server.R#178] 
112: <reactive:m.leapsLM> [C:\R\Application/server.R#69] . 

  lm.call <- object$call
  lm.call[[2]][[3]] <- rhs #error here

object$call must return

regsubsets(y ~ (.), data = m.inputMod(), nbest = 1, nvmax = 6, 
really.big = bigSearch)

,but it return <reactive:m.leaps>(...) I'm just want to make web UI. Only server script working correctly without <- renderPlot({})