How to reproduce:

Use Properties Tool. This tool targets content, and do not support multi-selection

• Open the search tool
  • Make a search with several contents
  • Select one content, and open its Properties tool
    • The tool is opened and displays the selected content's properties -> OK
  • Select a second content
    • The Properties tool dispalys a message to inform that multi-selection is not supported => OK
• Select a Page containing several contents (in Sitemap by exemple)
  • The properties tool displays the properties of the selected page's first content => KO
  • The properties tool should displays the message explainiing that multi-selection is not supported, as several contents are actually selected (all contents of the selected page)