Do not use set_text of Many2One and Reference when setting only string

changeset 13d81b52b4c4 replaced some direct call to wid_text.set_text by the
set_text but it set_text on Reference expect to receive a tuple (from
get_client). So when set_text is called just to clear or update the wid_text
it loose the selection of Reference.
Indeed as most of the time, it is called with an empty string, there is no
need to set the position of the entry.

issue8114
review54541002

tryton/gui/window/view_form/view/form_gtk/many2one.py

@@ -128,7 +128,7 @@ class Many2One(Widget):
                         self.field.set_client(self.record,
                             self.value_from_id(*result[0]), force_change=True)
                     else:
-                        self.set_text('')
+                        self.wid_text.set_text('')
                     self.focus_out = True
                     self.changed = True
 
@@ -251,7 +251,7 @@ class Many2One(Widget):
                 and editable
                 and event.keyval in (gtk.keysyms.Delete,
                     gtk.keysyms.BackSpace)):
-            self.set_text('')
+            self.wid_text.set_text('')
         return False
 
     def sig_changed(self, *args):
@@ -270,7 +270,7 @@ class Many2One(Widget):
                 # in such case, the original text should not be restored
                 if not self.wid_text.get_text():
                     # Restore text and position after display
-                    self.set_text(text)
+                    self.wid_text.set_text(text)
                     self.wid_text.set_position(position)
             gobject.idle_add(clean)
         return False
@@ -281,7 +281,7 @@ class Many2One(Widget):
     def set_value(self):
         if self.field.get_client(self.record) != self.wid_text.get_text():
             self.field.set_client(self.record, self.value_from_id(None, ''))
-            self.set_text('')
+            self.wid_text.set_text('')
 
     def set_text(self, value):
         if not value:
@@ -297,7 +297,7 @@ class Many2One(Widget):
         self._set_completion()
 
         if not self.field:
-            self.set_text('')
+            self.set_text(None)
             self.changed = True
             return False
         self.set_text(self.field.get_client(self.record))

tryton/gui/window/view_form/view/form_gtk/reference.py

@@ -126,7 +126,7 @@ class Reference(Many2One, SelectionMixin, PopdownMixin):
             if (model != self.get_model()
                     or name != self.wid_text.get_text()):
                 self.field.set_client(self.record, None)
-                self.set_text('')
+                self.set_text(None)
 
     def set_text(self, value):
         if value: