Prevent ops on empty selection

Fixes https://gitlab.com/kicad/code/kicad/issues/10164

pcbnew/tools/edit_tool.cpp

@@ -1453,6 +1453,10 @@ int EDIT_TOOL::Rotate( const TOOL_EVENT& aEvent )
                 true /* prompt user regarding locked items */ );
     }
 
+    // Did we filter everything out?  If so, don't try to operate further
+    if( selection.Empty() )
+        return 0;
+
     updateModificationPoint( selection );
 
     VECTOR2I refPt = selection.GetReferencePoint();
@@ -2251,6 +2255,10 @@ bool EDIT_TOOL::updateModificationPoint( PCB_SELECTION& aSelection )
     if( m_dragging && aSelection.HasReferencePoint() )
         return false;
 
+    // Can't modify an empty group
+    if( aSelection.Empty() )
+        return false;
+
     // When there is only one item selected, the reference point is its position...
     if( aSelection.Size() == 1 )
     {