Do not update value when selecting

We are meant to update only the temparary value not the symbol actual

Fixes https://gitlab.com/kicad/code/kicad/issues/21776

eeschema/sch_reference_list.cpp

@@ -771,10 +771,12 @@ SCH_REFERENCE::SCH_REFERENCE( SCH_SYMBOL* aSymbol, const SCH_SHEET_PATH& aSheetP
 
     m_numRef = -1;
 
-    if( aSymbol->GetValue( false, &aSheetPath, false ).IsEmpty() )
-        aSymbol->SetValueFieldText( wxT( "~" ) );
+    wxString value = aSymbol->GetValue( false, &aSheetPath, false );
 
-    m_value = aSymbol->GetValue( false, &aSheetPath, false );
+    if( value.IsEmpty() )
+        value = wxT( "~" );
+
+    m_value = value;
 }
 
 

qa/tests/eeschema/test_sch_reference_list.cpp

@@ -297,4 +297,31 @@ BOOST_AUTO_TEST_CASE( ReannotateDuplicates )
 }
 
 
+BOOST_AUTO_TEST_CASE( ReferenceListDoesNotMutateEmptyValue )
+{
+    loadTestCase( "test_multiunit_reannotate", {} );
+
+    SCH_SHEET_PATH sheetPath = m_schematic->CurrentSheet();
+    SCH_SYMBOL*    symbol = nullptr;
+
+    for( SCH_ITEM* item : sheetPath.LastScreen()->Items().OfType( SCH_SYMBOL_T ) )
+    {
+        symbol = static_cast<SCH_SYMBOL*>( item );
+        break;
+    }
+
+    BOOST_REQUIRE( symbol != nullptr );
+
+    symbol->SetValueFieldText( wxEmptyString );
+    BOOST_REQUIRE( symbol->GetValue( false, &sheetPath, false ).IsEmpty() );
+
+    SCH_REFERENCE_LIST refs;
+    sheetPath.AppendSymbol( refs, symbol );
+
+    BOOST_CHECK( symbol->GetValue( false, &sheetPath, false ).IsEmpty() );
+    BOOST_REQUIRE_EQUAL( refs.GetCount(), 1 );
+    BOOST_CHECK_EQUAL( refs[0].GetValue(), wxT( "~" ) );
+}
+
+
 BOOST_AUTO_TEST_SUITE_END()