Fix #16449: Viewport doesn't close when switching tabs

distribution/changelog.txt

@@ -34,6 +34,7 @@
 - Fix: [#16162] Go Karts speeds are not correctly randomised, they only go very fast or very slow.
 - Fix: [#16188] Medium-size banked turns on the Twister and Vertical Roller Coaster have incorrect support placement (partly original bug). 
 - Fix: [#16327] Crash on malformed network packet.
+- Fix: [#16449] [Plugin] Viewport doesn't hide when switching tabs.
 
 0.3.5.1 (2021-11-21)
 ------------------------------------------------------------------------

src/openrct2-ui/scripting/CustomWindow.cpp

@@ -807,6 +807,14 @@ namespace OpenRCT2::Ui::Windows
                         }
                     }
                 }
+                else
+                {
+                    RemoveViewport();
+                }
+            }
+            else
+            {
+                RemoveViewport();
             }
         }