fix 2 issues related to SCH_GLOBALLABEL items:

- Ensure the first field in m_fields has id = 0 to be seen has hypertext
(it was not the case after reading a .kicad_sch file)
- when converting this item to another label/text, remove this special Field
from the copied field list to the converted label.

eeschema/sch_plugins/kicad/sch_sexpr_parser.cpp

@@ -61,6 +61,7 @@
 #include <progress_reporter.h>
 #include <sch_shape.h>
 
+
 using namespace TSCHEMATIC_T;
 
 
@@ -1948,7 +1949,6 @@ SCH_FIELD* SCH_SEXPR_PARSER::parseSchField( SCH_ITEM* aParent )
 
     std::unique_ptr<SCH_FIELD> field = std::make_unique<SCH_FIELD>( VECTOR2I(-1,-1), -1,
                                                                     aParent, name );
-
     field->SetText( value );
     field->SetVisible( true );
 
@@ -3858,6 +3858,10 @@ SCH_TEXT* SCH_SEXPR_PARSER::parseSchText()
                      || field->GetInternalName() == wxT( "Intersheetrefs" ) ) ) // Current name
             {
                 SCH_GLOBALLABEL* label = static_cast<SCH_GLOBALLABEL*>( text.get() );
+                // Ensure the Id of this special and first field is 0, needed by
+                // SCH_FIELD::IsHypertext() test
+                field->SetId( 0 );
+
                 label->GetFields()[0] = *field;
             }
             else

eeschema/tools/sch_edit_tool.cpp

@@ -2165,8 +2165,23 @@ int SCH_EDIT_TOOL::ChangeTextType( const TOOL_EVENT& aEvent )
             SCH_LABEL_BASE* new_label = dynamic_cast<SCH_LABEL_BASE*>( newtext );
 
             if( label && new_label )
+            {
                 new_label->AddFields( label->GetFields() );
 
+                // A SCH_GLOBALLABEL has a specific field, that has no meaning for
+                // other labels, and expected to be the first field in list.
+                // It is the first field in list for this kind of label
+                // So remove field named "Intersheetrefs" if exists for other labels
+                int min_idx = new_label->Type() == SCH_GLOBAL_LABEL_T ? 1 : 0;
+                std::vector<SCH_FIELD>& fields = new_label->GetFields();
+
+                for( int ii = fields.size()-1; ii >= min_idx; ii-- )
+                {
+                    if( fields[ii].GetCanonicalName() == wxT( "Intersheetrefs" ) )
+                        fields.erase( fields.begin() + ii );
+                }
+            }
+
             if( selected )
                 m_toolMgr->RunAction( EE_ACTIONS::removeItemFromSel, true, item );