Handle hidden attribute in fp-lib-table

Fixes https://gitlab.com/kicad/code/kicad/-/issues/13689

common/fp_lib_table.cpp

@@ -184,6 +184,12 @@ void FP_LIB_TABLE::Parse( LIB_TABLE_LEXER* in )
                 row->SetEnabled( false );
                 break;
 
+            case T_hidden:
+                // Hiding footprint libraries is not yet supported.  Unclear what path can set this
+                // attribute, but clear it on load.
+                row->SetVisible();
+                break;
+
             default:
                 in->Unexpected( tok );
             }

pcbnew/dialogs/panel_fp_lib_table.cpp

@@ -581,6 +581,10 @@ bool PANEL_FP_LIB_TABLE::verifyTables()
                 // set the trimmed values back into the table so they get saved to disk.
                 model->SetValue( r, COL_NICKNAME, nick );
                 model->SetValue( r, COL_URI, uri );
+
+                // Make sure to not save a hidden flag
+                model->SetValue( r, COL_VISIBLE, wxS( "1" ) );
+
                 ++r;        // this row was OK.
             }
         }