Fix memory leaks, sizes for image generation

Sources/Generator/Content/Element.swift

@@ -312,11 +312,12 @@ extension Element {
 
     var linkedElements: [LinkedElement] {
         let items = sortedItems
-        return items.enumerated().map { i, element in
+        let connected = items.enumerated().map { i, element in
             let previous = i+1 < items.count ? items[i+1] : nil
             let next = i > 0 ? items[i-1] : nil
             return (previous, element, next)
         }
+        return connected + elements.filter { !$0.state.isShownInOverview }.map { (nil, $0, nil )}
     }
 
     /**