Created attachment 272612 [details] [review]
Fix assertion/crash

If gtk_radio_menu_item_set_group() is passed the same group returned by gtk_radio_menu_item_get_group() for the same widget, GTK+ prints a warning (or crashes if compiled with --enable-debug=no).  Calling gtk_radio_menu_item_set_group() in this case is pointless and should be a no-op, but it should not cause a crash.

Example code to reproduce:

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#include <gtk/gtk.h>

int main (void)
{
    gtk_init (NULL, NULL);

    GtkWidget * radio1 = gtk_radio_menu_item_new (NULL);

    GSList * group = gtk_radio_menu_item_get_group ((GtkRadioMenuItem *) radio1);
    gtk_radio_menu_item_set_group ((GtkRadioMenuItem *) radio1, group);

    return 0;
}

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This is currently causing Galculator (the GTK3 version) to crash on startup.  Evidently GtkBuilder processes the "group" property twice in some cases (which is probably a separate bug).

Snippet from running "GTK_DEBUG=builder galculator":

--------------------

<child>
<object class="GtkRadioMenuItem" id="hex">
<property name="visible">
</property>
<property name="can_focus">
</property>
<property name="use_action_appearance">
</property>
<property name="label" translatable="yes">
</property>
<property name="use_underline">
</property>
<property name="group">
</property>
<accelerator key="H" signal="activate" modifiers="GDK_CONTROL_MASK">
created hex of type GtkRadioMenuItem
set hex: visible = TRUE
set hex: can-focus = FALSE
set hex: use-action-appearance = FALSE
set hex: label = "_Hexadecimal"
set hex: use-underline = TRUE
set hex: group = ((GtkRadioMenuItem*) 0xe498b0)
</accelerator>
<signal name="toggled" handler="on_hex_toggled" swapped="no">
</signal>
</object>

(galculator:13925): Gtk-CRITICAL **: gtk_radio_menu_item_set_group: assertion '!g_slist_find (group, radio_menu_item)' failed
set hex: group = ((GtkRadioMenuItem*) 0xe498b0)
set hex: use-underline = TRUE
set hex: label = "_Hexadecimal"
set hex: use-action-appearance = FALSE
set hex: can-focus = FALSE
set hex: visible = TRUE
</child>
adding hex to base_units_menu

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