Misc: Fix GObject property types for GLabel::xalign/yalign properties

When running under valgrind, it claims that there's used uninitialized
memory, which is set as GObject property in the code. It's for
GtkLabel::xalign. The problem was that the value in the code is
an integer, but the property itself expects float type. This fixes
the place and where a floating point is already used it annotates
the value to be float, not a double.

src/gui/views/gcal-agenda-view.c

@@ -387,7 +387,7 @@ update_header (GtkListBoxRow *row,
 
   header = g_object_new (GTK_TYPE_LABEL,
                          "label", label,
-                         "xalign", 0,
+                         "xalign", 0.0f,
                          NULL);
   gtk_widget_add_css_class (header, "caption-heading");