Eeschema: fix crash when adding a new SCH_HIERLABEL.

The crash was due to use a temporary parent in SCH_LABEL_BASE::SetLabelShape()
The parent must be a SCH_SCREEN and is now tested before use.
It is also fixed and set to the current SCH_SCREEN at creation.

Fixes https://gitlab.com/kicad/code/kicad/-/issues/21786

common/eda_item.cpp

@@ -412,6 +412,7 @@ static struct EDA_ITEM_DESC
             .Undefined( TYPE_NOT_INIT )
             .Map( NOT_USED,                wxT( "<not used>" ) )
             .Map( SCREEN_T,                _HKI( "Screen" ) )
+            .Map( SCHEMATIC_T,             _HKI( "Schematic" ) )
 
             .Map( PCB_FOOTPRINT_T,         _HKI( "Footprint" ) )
             .Map( PCB_PAD_T,               _HKI( "Pad" ) )

eeschema/sch_label.cpp

@@ -331,7 +331,7 @@ void SCH_LABEL_BASE::SetLabelShape( LABEL_SHAPE aShape )
     if( Type() == SCH_HIER_LABEL_T )
     {
         SCH_HIERLABEL* label = static_cast<SCH_HIERLABEL*>( this );
-        SCH_SCREEN*    screen = static_cast<SCH_SCREEN*>( label->GetParent() );
+        SCH_SCREEN*    screen = dynamic_cast<SCH_SCREEN*>( label->GetParent() );
 
         if( screen )
         {

eeschema/tools/sch_drawing_tools.cpp

@@ -1784,11 +1784,13 @@ bool SCH_DRAWING_TOOLS::createNewLabel( const VECTOR2I& aPosition, int aType,
         break;
 
     default:
-        wxFAIL_MSG( "SCH_EDIT_FRAME::CreateNewText() unknown layer type" );
+        wxFAIL_MSG( "SCH_DRAWING_TOOLS::createNewLabel() unknown label type" );
         return false;
     }
 
-    labelItem->SetParent( schematic );
+    // The normal parent is the current screen for these labels, set by SCH_SCREEN::Append()
+    // but it is also used during placement for SCH_HIERLABEL before beeing appended
+    labelItem->SetParent( m_frame->GetScreen() );
 
     labelItem->SetTextSize( VECTOR2I( settings.m_DefaultTextSize, settings.m_DefaultTextSize ) );