*_unref: Always expect a valid pointer

Those functions have been very inconsistent in that way that some
happily accepted a NULL pointer and others didn't.
Signed-off-by: Michael Tremer <michael.tremer@ipfire.org>

src/country-list.c

@@ -81,9 +81,6 @@ static void loc_country_list_free(struct loc_country_list* list) {
 }
 
 LOC_EXPORT struct loc_country_list* loc_country_list_unref(struct loc_country_list* list) {
-	if (!list)
-		return NULL;
-
 	if (--list->refcount > 0)
 		return list;
 

src/libloc.c

@@ -103,9 +103,6 @@ LOC_EXPORT struct loc_ctx* loc_ref(struct loc_ctx* ctx) {
 }
 
 LOC_EXPORT struct loc_ctx* loc_unref(struct loc_ctx* ctx) {
-	if (!ctx)
-		return NULL;
-
 	if (--ctx->refcount > 0)
 		return NULL;
 

src/network-list.c

@@ -83,9 +83,6 @@ static void loc_network_list_free(struct loc_network_list* list) {
 }
 
 LOC_EXPORT struct loc_network_list* loc_network_list_unref(struct loc_network_list* list) {
-	if (!list)
-		return NULL;
-
 	if (--list->refcount > 0)
 		return list;
 

src/network.c

@@ -116,9 +116,6 @@ static void loc_network_free(struct loc_network* network) {
 }
 
 LOC_EXPORT struct loc_network* loc_network_unref(struct loc_network* network) {
-	if (!network)
-		return NULL;
-
 	if (--network->refcount > 0)
 		return network;
 
@@ -856,9 +853,6 @@ static void loc_network_tree_node_free(struct loc_network_tree_node* node) {
 }
 
 struct loc_network_tree_node* loc_network_tree_node_unref(struct loc_network_tree_node* node) {
-	if (!node)
-		return NULL;
-
 	if (--node->refcount > 0)
 		return node;
 

src/test-network.c

@@ -302,7 +302,6 @@ int main(int argc, char** argv) {
 		fprintf(stderr, "Could look up 2001:db8:fffe:1::, but I shouldn't\n");
 		exit(EXIT_FAILURE);
 	}
-	loc_network_unref(network1);
 
 	const struct bit_length_test {
 		const char* network;