resource-container: fix segmentation fault if configuration is not initialized

resource-container: fix segmentation fault if configuration is not initialized

When the configuration is not initialized, for example because the
demon does not use the configuration, this program will run into a
segmentation fault when a new resource gets registered.

Change-Id: I1a6b4b468bdc74136e91ffb5c5dbc3c4d276fe15
Signed-off-by: Hauke Mehrtens <hauke.mehrtens@lantiq.com>
Reviewed-on: https://gerrit.iotivity.org/gerrit/4151
Tested-by: jenkins-iotivity <jenkins-iotivity@opendaylight.org>
Reviewed-by: Markus Jung <markus.jung85@gmail.com>
Reviewed-by: Madan Lanka <lanka.madan@samsung.com>