我如何确保在我的闪亮应用程序中出现renderPlot之前的观察?

I have a shiny application with two selectInputs (L1 and L2) with an observer that updates L2 based on the selection of L1 using updateSelectInput. I also have a renderPlot output that depends on both selections. The problem I face is that whenever I change L1, the renderPlot gets called twice, once with the old value of L2 and once with the new value (set in updateSelectInput). My code is below:I have a shiny application with two selectInput