Fixed divide by zero segault (#461)

Check if inner_size is less than 1 to prevent divide by 0 segfault.

Co-authored-by: Arthur Sonzogni <sonzogniarthur@gmail.com>

src/ftxui/dom/scroll_indicator.cpp

@@ -40,6 +40,9 @@ Element vscroll_indicator(Element child) {
       const Box& stencil = screen.stencil;
 
       int size_inner = box_.y_max - box_.y_min;
+      if (size_inner <= 0) {
+        return;
+      }
       int size_outter = stencil.y_max - stencil.y_min + 1;
       if (size_outter >= size_inner) {
         return;