gst-libs/gst/colorbalance/colorbalancechannel.c: Adding safety check in dispose method.

gst-libs/gst/colorbalance/colorbalancechannel.c: Adding safety check in dispose method.

Original commit message from CVS:
2004-01-12  Julien MOUTTE <julien@moutte.net>

* gst-libs/gst/colorbalance/colorbalancechannel.c:
(gst_color_balance_channel_dispose): Adding safety check in dispose
method.
* sys/xvimage/xvimagesink.c: (gst_xvimagesink_xcontext_get),
(gst_xvimagesink_xcontext_clear),
(gst_xvimagesink_interface_supported),
(gst_xvimagesink_colorbalance_list_channels),
(gst_xvimagesink_colorbalance_set_value),
(gst_xvimagesink_colorbalance_get_value),
(gst_xvimagesink_colorbalance_init), (gst_xvimagesink_get_type):
Adding colorbalance interface support to set XV parameters such as
HUE, BRIGHTNESS, CONTRAST, SATURATION.
* sys/xvimage/xvimagesink.h: Adding the channels list for colorbalance
interface.