[libgweather] weather: Add documentation note about 0 update timestamp

[Bastien Nocera <hadess src gnome org>]

commit 825dc903605eb165c8ad9f4e878e496812f33412
Author: Philip Chimento <philip chimento gmail com>
Date:   Tue Nov 19 19:45:55 2019 +0000

    weather: Add documentation note about 0 update timestamp
    
    GNOME Shell, for one, was ignoring the possibility that the update
    timestamp could be 0. It seems useful to note it in the documentation.

 libgweather/gweather-weather.c | 2 ++
 1 file changed, 2 insertions(+)
---
diff --git a/libgweather/gweather-weather.c b/libgweather/gweather-weather.c
index 7ec0cdb..0a9626b 100644
--- a/libgweather/gweather-weather.c
+++ b/libgweather/gweather-weather.c
@@ -1914,6 +1914,8 @@ gweather_info_get_value_apparent (GWeatherInfo *info, GWeatherTemperatureUnit un
  * @info: a #GWeatherInfo
  * @value: (out) (type glong): the time @info was last updated
  *
+ * Note that @value may be 0 if @info has not yet been updated.
+ *
  * Returns: TRUE is @value is valid, FALSE otherwise.
  */
 gboolean