Special handling for presence of Ref or Value in groups.

Fixes https://gitlab.com/kicad/code/kicad/issues/6677

pcbnew/footprint.cpp

@@ -94,13 +94,16 @@ FOOTPRINT::FOOTPRINT( const FOOTPRINT& aFootprint ) :
     m_thermalWidth = aFootprint.m_thermalWidth;
     m_thermalGap = aFootprint.m_thermalGap;
 
+    std::map<BOARD_ITEM*, BOARD_ITEM*> ptrMap;
+
     // Copy reference and value.
     m_reference = new FP_TEXT( *aFootprint.m_reference );
     m_reference->SetParent( this );
+    ptrMap[ aFootprint.m_reference ] = m_reference;
+
     m_value = new FP_TEXT( *aFootprint.m_value );
     m_value->SetParent( this );
-
-    std::map<BOARD_ITEM*, BOARD_ITEM*> ptrMap;
+    ptrMap[ aFootprint.m_value ] = m_value;
 
     // Copy pads
     for( PAD* pad : aFootprint.Pads() )

pcbnew/tools/edit_tool.cpp

@@ -1396,6 +1396,14 @@ int EDIT_TOOL::Remove( const TOOL_EVENT& aEvent )
             {
                 if( bItem->GetParent() && bItem->GetParent()->Type() == PCB_FOOTPRINT_T )
                 {
+                    // Silently ignore delete of Reference or Value if they happen to be in
+                    // group.
+                    if( bItem->Type() == PCB_FP_TEXT_T )
+                    {
+                        if( static_cast<FP_TEXT*>( bItem )->GetType() != FP_TEXT::TEXT_is_DIVERS )
+                            return;
+                    }
+
                     m_commit->Modify( bItem->GetParent() );
                     getView()->Remove( bItem );
                     bItem->GetParent()->Remove( bItem );