Fix accidentally inverted condition (for Group stack layout participation check)

The check was backwards which meant that even Groups with no visible
children would participate in stack layout participation, so wrapping
a bunch of children in a Group wasn't a layout preserving operation.

Author: stackotter

Sources/SwiftCrossUI/LayoutSystem.swift

@@ -233,16 +233,19 @@ public enum LayoutSystem {
             }
         }
 
+        // If the stack has been told to inherit its stack layout participation
+        // and all of its children are hidden, then the stack itself also
+        // shouldn't participate in stack layouts.
+        let shouldGetIgnoredInStackLayouts =
+            inheritStackLayoutParticipation && isHidden.allSatisfy { $0 }
         return ViewSize(
             size: size,
             idealSize: idealSize,
             minimumWidth: minimumWidth,
             minimumHeight: minimumHeight,
             maximumWidth: maximumWidth,
             maximumHeight: maximumHeight,
-            participateInStackLayoutsWhenEmpty:
-                inheritStackLayoutParticipation
-                && isHidden.allSatisfy { $0 }
+            participateInStackLayoutsWhenEmpty: !shouldGetIgnoredInStackLayouts
         )
     }
 }