[gnome-software] gs-updates-section: Avoid crash when switching modes

[Kalev Lember <klember src gnome org>]

commit 8e2cd118a5dd0efc8553feaf3347ebc25f8545a9
Author: Philip Withnall <withnall endlessm com>
Date:   Fri Oct 4 18:20:00 2019 +0100

    gs-updates-section: Avoid crash when switching modes
    
    Depending on how the `_list_header_func()` is called for different
    orders of rows and updates, it’s possible for the `self->section_header`
    to be set as the header for row A. In the next cycle of updates, if it’s
    set as the header for row B, and then the header is updated for row A
    (to be a normal separator), GTK+ will unparent the
    `self->section_header` and leave it parentless.
    
    This causes the following critical:
    ```
    gtk_widget_realize: assertion 'widget->priv->anchored || GTK_IS_INVISIBLE (widget)' failed
    **
    Gtk:ERROR:../../../../gtk/gtkwidget.c:12348:gtk_widget_real_map: assertion failed: 
(_gtk_widget_get_realized (widget))
    ```
    
    The real fix for this is in GTK+, but in the meantime, we can improve
    the situation by using gtk_widget_unparent() (simpler), and only call it
    if the row’s header is going to change, rather than unconditionally
    unparenting the `self->section_header`.
    
    Signed-off-by: Philip Withnall <withnall endlessm com>

 src/gs-updates-section.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)
---
diff --git a/src/gs-updates-section.c b/src/gs-updates-section.c
index 2743ecc9..c4567b12 100644
--- a/src/gs-updates-section.c
+++ b/src/gs-updates-section.c
@@ -489,9 +489,9 @@ _list_header_func (GtkListBoxRow *row, GtkListBoxRow *before, gpointer user_data
 
        /* section changed */
        if (before == NULL) {
-               GtkWidget *parent;
-               if ((parent = gtk_widget_get_parent (GTK_WIDGET (self->section_header))) != NULL)
-                       gtk_container_remove (GTK_CONTAINER (parent), GTK_WIDGET (self->section_header));
+               if (gtk_list_box_row_get_header (row) != self->section_header) {
+                       gtk_widget_unparent (self->section_header);
+               }
                header = self->section_header;
        } else {
                header = gtk_separator_new (GTK_ORIENTATION_HORIZONTAL);