Program: 51954
Project: 51954
Buggy source:
private void applyOverlay(Document doc){
  this.document=getDocumentRoot();
  for (  XulComponent overlay : doc.getChildNodes()) {
    for (    XulComponent child : overlay.getChildNodes()) {
      XulComponent sourceDocumentNodeMatch;
      String childId=child.getId();
      if (childId != null && (sourceDocumentNodeMatch=this.document.getElementById(childId)) != null) {
        if (child.getRemoveelement()) {
          sourceDocumentNodeMatch.getParent().removeChild(sourceDocumentNodeMatch);
          continue;
        }
        sourceDocumentNodeMatch.adoptAttributes(child);
        for (        XulComponent overlayChild : child.getChildNodes()) {
          int position=overlayChild.getPosition();
          String insertBefore=overlayChild.getInsertbefore();
          String insertAfter=overlayChild.getInsertafter();
          XulContainer sourceContainer=((XulContainer)sourceDocumentNodeMatch);
          if (position > -1) {
            sourceContainer.addChildAt(overlayChild,position);
          }
 else           if (insertBefore != null) {
            XulComponent relativeTo=document.getElementById(insertBefore);
            if (relativeTo != null && sourceDocumentNodeMatch.getChildNodes().contains(relativeTo)) {
              int relativePos=sourceDocumentNodeMatch.getChildNodes().indexOf(relativeTo);
              relativePos--;
              Math.abs(relativePos);
              sourceContainer.addChildAt(overlayChild,relativePos);
            }
 else {
              sourceContainer.addChild(overlayChild);
            }
          }
 else           if (insertAfter != null) {
            XulComponent relativeTo=document.getElementById(insertAfter);
            if (relativeTo != null && sourceDocumentNodeMatch.getChildNodes().contains(relativeTo)) {
              int relativePos=sourceDocumentNodeMatch.getChildNodes().indexOf(relativeTo);
              relativePos++;
              sourceContainer.addChildAt(overlayChild,relativePos);
            }
 else {
              sourceContainer.addChild(overlayChild);
            }
          }
 else {
            sourceContainer.addChild(overlayChild);
          }
        }
      }
    }
  }
}

Fixed version (ground truth):
private void applyOverlay(Document doc){
  this.document=getDocumentRoot();
  for (  XulComponent overlay : doc.getChildNodes()) {
    for (    XulComponent child : overlay.getChildNodes()) {
      XulComponent sourceDocumentNodeMatch;
      String childId=child.getId();
      if (childId != null && (sourceDocumentNodeMatch=this.document.getElementById(childId)) != null) {
        if (child.getRemoveelement()) {
          sourceDocumentNodeMatch.getParent().removeChild(sourceDocumentNodeMatch);
          continue;
        }
        sourceDocumentNodeMatch.adoptAttributes(child);
        for (        XulComponent overlayChild : child.getChildNodes()) {
          int position=overlayChild.getPosition();
          String insertBefore=overlayChild.getInsertbefore();
          String insertAfter=overlayChild.getInsertafter();
          XulContainer sourceContainer=((XulContainer)sourceDocumentNodeMatch);
          ((AbstractGwtXulComponent)overlayChild).setXulDomContainer(this);
          if (position > -1) {
            sourceContainer.addChildAt(overlayChild,position);
          }
 else           if (insertBefore != null) {
            XulComponent relativeTo=document.getElementById(insertBefore);
            if (relativeTo != null && sourceDocumentNodeMatch.getChildNodes().contains(relativeTo)) {
              int relativePos=sourceDocumentNodeMatch.getChildNodes().indexOf(relativeTo);
              relativePos--;
              Math.abs(relativePos);
              sourceContainer.addChildAt(overlayChild,relativePos);
            }
 else {
              sourceContainer.addChild(overlayChild);
            }
          }
 else           if (insertAfter != null) {
            XulComponent relativeTo=document.getElementById(insertAfter);
            if (relativeTo != null && sourceDocumentNodeMatch.getChildNodes().contains(relativeTo)) {
              int relativePos=sourceDocumentNodeMatch.getChildNodes().indexOf(relativeTo);
              relativePos++;
              sourceContainer.addChildAt(overlayChild,relativePos);
            }
 else {
              sourceContainer.addChild(overlayChild);
            }
          }
 else {
            sourceContainer.addChild(overlayChild);
          }
        }
      }
    }
  }
}