Don't show actors of minimized scratch windows

Specifically fixes bug where whole scratch layer become visible (but only the
actors) when reloading (or disable/enable cycle) when at least on scratch window
was active.

This also sometimes crashed gnome-shell (confirmed on v3.28.3 - ubuntu 18.04)

Also remove some code who seem to partly work around the problem

scratch.js

@@ -21,7 +21,9 @@ function makeScratch(metaWindow) {
     metaWindow[float] = true;
     metaWindow.make_above();
     metaWindow.stick();
-    Tiling.showWindow(metaWindow);
+
+    if (!metaWindow.minimized)
+        Tiling.showWindow(metaWindow);
 
     let monitor = focusMonitor();
     if (monitor.clickOverlay)

tiling.js

@@ -1702,11 +1702,6 @@ function enable() {
             s.selectedWindow && ensureViewport(s.selectedWindow, s, true);
             s.monitor.clickOverlay.show();
         });
-
-        if (!Scratch.isScratchActive()) {
-            Scratch.getScratchWindows().forEach(
-                w => w.get_compositor_private().hide());
-        }
     }
 
     if (Main.layoutManager._startingUp) {
@@ -2525,7 +2520,7 @@ function slurp(metaWindow) {
     }
 
     space[to].push(metaWindowToSlurp)
-    
+
     { // Remove the slurped window
         let column = space[from];
         let row = column.indexOf(metaWindowToSlurp);