[fix] unsafe debugToolWindow access (flutter#8395)

It's not safe to assume that the debug window is visible when running/debugging (from the toolbar), so we need to add a check. (Note that something similar is already done for the run window.)

Fixes: flutter#8391

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Author: pq

src/io/flutter/toolwindow/ToolWindowBadgeUpdater.java

@@ -42,9 +42,12 @@ public static void updateBadgedIcon(FlutterApp app, Project project) {
     }
     else if (app.getMode() == RunMode.DEBUG) {
       manager.invokeLater(() -> {
-        Icon baseIcon = AllIcons.Toolwindows.ToolWindowDebugger;
-        BadgeIcon iconWithBadge = new BadgeIcon(baseIcon, BADGE_PAINT);
-        Objects.requireNonNull(debugToolWindow).setIcon(iconWithBadge);
+        // https://github.com/flutter/flutter-intellij/issues/8391
+        if (debugToolWindow != null) {
+          Icon baseIcon = AllIcons.Toolwindows.ToolWindowDebugger;
+          BadgeIcon iconWithBadge = new BadgeIcon(baseIcon, BADGE_PAINT);
+          runToolWindow.setIcon(iconWithBadge);
+        }
       });
     }
   }