Program: 65555
Project: 65555
Buggy source:
/** 
 * Returns the object can be deleted. If the parent can be deleted, the children will be skippedl
 * @param source single or multiple objects
 */
protected boolean canDrop(Object source){
  if (SessionHandleAdapter.getInstance().getReportDesignHandle() == null) {
    return false;
  }
  if (source == null) {
    return false;
  }
  if (source instanceof List) {
    return canDrop(((List)source).toArray());
  }
  if (source instanceof StructuredSelection) {
    return canDrop(((StructuredSelection)source).toArray());
  }
  if (source instanceof Object[]) {
    Object[] array=(Object[])source;
    if (array.length == 0) {
      return false;
    }
    for (int i=0; i < array.length; i++) {
      if (DNDUtil.checkContainerExists(array[i],array))       continue;
      if (array[i] instanceof MasterPageHandle) {
        int masterPageCount=SessionHandleAdapter.getInstance().getReportDesignHandle().getMasterPages().getCount();
        for (int j=0; j < array.length; j++) {
          if (array[j] instanceof MasterPageHandle)           masterPageCount--;
        }
        if (masterPageCount == 0)         return false;
      }
      if (!canDrop(array[i]))       return false;
    }
    return true;
  }
  source=DNDUtil.unwrapToModel(source);
  if (source instanceof SlotHandle) {
    SlotHandle slot=(SlotHandle)source;
    DesignElementHandle handle=slot.getElementHandle();
    return slot.getContents().size() > 0 && handle != null && handle.canDrop() && canDrop(slot.getContents());
  }
  if (source instanceof EmbeddedImageHandle) {
    return true;
  }
  if (source instanceof ExtendedItemHandle) {
    Object dropValidator=Platform.getAdapterManager().getAdapter((ExtendedItemHandle)source,DeleteCommand.class);
    if (dropValidator instanceof IDropValidator && ((IDropValidator)dropValidator).accpetValidator())     return ((IDropValidator)dropValidator).canDrop();
  }
  if (source instanceof CellHandle) {
    return ((CellHandle)source).getContent().getContents().size() > 0 && ((CellHandle)source).canDrop();
  }
  if (source instanceof MasterPageHandle) {
    if (SessionHandleAdapter.getInstance().getReportDesignHandle().getMasterPages().getCount() > 1) {
      return true;
    }
    return false;
  }
 else   if (source instanceof ModuleHandle) {
    return false;
  }
 else   if (source instanceof DesignElementHandle) {
    return ((DesignElementHandle)source).canDrop();
  }
 else   if (source instanceof LibraryHandle) {
    if (((LibraryHandle)source).getHostHandle() != null)     return true;
 else     return false;
  }
 else   if (source instanceof CssStyleSheetHandle) {
    DesignElementHandle elementHandle=((CssStyleSheetHandle)source).getContainerHandle();
    if (elementHandle instanceof ReportDesignHandle) {
      return ((ReportDesignHandle)elementHandle).canDropCssStyleSheet((CssStyleSheetHandle)source);
    }
 else     if (elementHandle instanceof AbstractThemeHandle) {
      return ((AbstractThemeHandle)elementHandle).canDropCssStyleSheet((CssStyleSheetHandle)source);
    }
 else {
      return false;
    }
  }
 else   return false;
}

Fixed version (ground truth):
/** 
 * Returns the object can be deleted. If the parent can be deleted, the children will be skippedl
 * @param source single or multiple objects
 */
protected boolean canDrop(Object source){
  if (SessionHandleAdapter.getInstance().getReportDesignHandle() == null) {
    return false;
  }
  if (source == null) {
    return false;
  }
  if (source instanceof List) {
    return canDrop(((List)source).toArray());
  }
  if (source instanceof StructuredSelection) {
    return canDrop(((StructuredSelection)source).toArray());
  }
  if (source instanceof Object[]) {
    Object[] array=(Object[])source;
    if (array.length == 0) {
      return false;
    }
    for (int i=0; i < array.length; i++) {
      if (DNDUtil.checkContainerExists(array[i],array))       continue;
      if (array[i] instanceof MasterPageHandle) {
        int masterPageCount=SessionHandleAdapter.getInstance().getReportDesignHandle().getMasterPages().getCount();
        for (int j=0; j < array.length; j++) {
          if (array[j] instanceof MasterPageHandle)           masterPageCount--;
        }
        if (masterPageCount == 0)         return false;
      }
      if (!canDrop(array[i]))       return false;
    }
    return true;
  }
  source=DNDUtil.unwrapToModel(source);
  if (source instanceof SlotHandle) {
    SlotHandle slot=(SlotHandle)source;
    DesignElementHandle handle=slot.getElementHandle();
    return slot.getContents().size() > 0 && handle != null && handle.canDrop() && canDrop(slot.getContents());
  }
  if (source instanceof EmbeddedImageHandle) {
    return true;
  }
  if (source instanceof ExtendedItemHandle) {
    Object dropValidator=Platform.getAdapterManager().getAdapter((ExtendedItemHandle)source,DeleteCommand.class);
    if (dropValidator instanceof IDropValidator && ((IDropValidator)dropValidator).accpetValidator())     return ((IDropValidator)dropValidator).canDrop();
  }
  if (source instanceof CellHandle) {
    return ((CellHandle)source).getContent().getContents().size() > 0 && ((CellHandle)source).canDrop();
  }
  if (source instanceof MasterPageHandle) {
    if (SessionHandleAdapter.getInstance().getReportDesignHandle().getMasterPages().getCount() > 1) {
      return true;
    }
    return false;
  }
 else   if (source instanceof ModuleHandle) {
    return false;
  }
 else   if (source instanceof DesignElementHandle) {
    return ((DesignElementHandle)source).canDrop();
  }
 else   if (source instanceof LibraryHandle) {
    if (((LibraryHandle)source).getHostHandle() != null)     return true;
 else     return false;
  }
 else   if (source instanceof CssStyleSheetHandle) {
    DesignElementHandle elementHandle=((CssStyleSheetHandle)source).getContainerHandle();
    if (elementHandle instanceof ReportDesignHandle) {
      return ((ReportDesignHandle)elementHandle).canDropCssStyleSheet((CssStyleSheetHandle)source);
    }
 else     if (elementHandle instanceof AbstractThemeHandle) {
      return ((AbstractThemeHandle)elementHandle).canDropCssStyleSheet((CssStyleSheetHandle)source);
    }
 else {
      return false;
    }
  }
 else   if (source instanceof ScriptObjectNode) {
    return true;
  }
 else   return false;
}