Passing a string to LIBRARY_TABLE's c'tor doesn't do what you think it does.

Also fixes nested tables being deleted out from under
the dialog.

Also fixes a bug where PANEL_DESIGN_BLOCK_LIB_TABLE
had fallen behind the the other two.

common/dialogs/panel_design_block_lib_table.cpp

@@ -245,10 +245,10 @@ protected:
 
     void openTable( const LIBRARY_TABLE_ROW& aRow ) override
     {
-        wxString uri = LIBRARY_MANAGER::ExpandURI( aRow.URI(), Pgm().GetSettingsManager().Prj() );
-        auto     nestedTable = std::make_unique<LIBRARY_TABLE>( uri, LIBRARY_TABLE_SCOPE::GLOBAL );
+        wxFileName fn( LIBRARY_MANAGER::ExpandURI( aRow.URI(), Pgm().GetSettingsManager().Prj() ) );
+        std::shared_ptr<LIBRARY_TABLE> child = std::make_shared<LIBRARY_TABLE>( fn, LIBRARY_TABLE_SCOPE::GLOBAL );
 
-        m_panel->AddTable( nestedTable.get(), aRow.Nickname(), true );
+        m_panel->OpenTable( child, aRow.Nickname() );
     }
 
     wxString getTablePreamble() override
@@ -261,7 +261,7 @@ protected:
 };
 
 
-void PANEL_DESIGN_BLOCK_LIB_TABLE::OpenTable( LIBRARY_TABLE* aTable, const wxString& aTitle )
+void PANEL_DESIGN_BLOCK_LIB_TABLE::OpenTable( const std::shared_ptr<LIBRARY_TABLE>& aTable, const wxString& aTitle )
 {
     for( int ii = 2; ii < (int) m_notebook->GetPageCount(); ++ii )
     {
@@ -276,7 +276,8 @@ void PANEL_DESIGN_BLOCK_LIB_TABLE::OpenTable( LIBRARY_TABLE* aTable, const wxStr
         }
     }
 
-    AddTable( aTable, aTitle, true );
+    m_nestedTables.push_back( aTable );
+    AddTable( aTable.get(), aTitle, true );
 
     // Something is pretty fishy with wxAuiNotebook::ChangeSelection(); on Mac at least it
     // results in a re-entrant call where the second call is one page behind.