fix build warnings

nua.c:1101:16: warning: address of array 'nh->nh_ds' will always evaluate to 'true' [-Wpointer-bool-conversion]
        if (nh && nh->nh_ds)
               ~~ ~~~~^~~~~
nua.c:1110:16: warning: address of array 'nh->nh_home' will always evaluate to 'true' [-Wpointer-bool-conversion]
        if (nh && nh->nh_home)
               ~~ ~~~~^~~~~~~
nua.c:1119:18: warning: address of array 'nua->nua_home' will always evaluate to 'true' [-Wpointer-bool-conversion]
        if (nua && nua->nua_home)
                ~~ ~~~~~^~~~~~~~
nua.c:1150:16: warning: address of array 'nh->nh_ds' will always evaluate to 'true' [-Wpointer-bool-conversion]
        if (nh && nh->nh_ds && nh->nh_ds->ds_usage) {
               ~~ ~~~~^~~~~

libsofia-sip-ua/nua/nua.c

@@ -89,7 +89,7 @@ su_log_t nua_log[] = { SU_LOG_INIT("nua", "NUA_DEBUG", SU_DEBUG) };
  * @param root            Pointer to a root object
  * @param callback        Pointer to event callback function
  * @param magic           Pointer to callback context
- * @param tag, value, ... List of tagged parameters
+ * @param tag, value, ... List of tagged parameters
  *
  * @retval !=NULL a pointer to a @nua stack object
  * @retval NULL upon an error
@@ -1098,7 +1098,7 @@ nua_handle_t *nua_handle_by_call_id(nua_t *nua, const char *call_id)
 /** Get leg from dialog. */
 const nta_leg_t *nua_get_dialog_state_leg(nua_handle_t *nh)
 {
-	if (nh && nh->nh_ds)
+	if (nh)
 		return nh->nh_ds->ds_leg;
 	else
 		return NULL;
@@ -1107,7 +1107,7 @@ const nta_leg_t *nua_get_dialog_state_leg(nua_handle_t *nh)
 /** Get su_home_t from nua handle. */
 su_home_t *nua_handle_get_home(nua_handle_t *nh)
 {
-	if (nh && nh->nh_home)
+	if (nh)
 		return nh->nh_home;
 	else
 		return NULL;
@@ -1116,7 +1116,7 @@ su_home_t *nua_handle_get_home(nua_handle_t *nh)
 /** Get su_home_t from nua. */
 su_home_t *nua_get_home(nua_t *nua)
 {
-	if (nua && nua->nua_home)
+	if (nua)
 		return nua->nua_home;
 	else
 		return NULL;
@@ -1147,7 +1147,7 @@ unsigned nua_handle_is_destroyed(nua_handle_t *nh)
 
 void nua_handle_dialog_usage_set_refresh_range(nua_handle_t *nh,
 	unsigned min, unsigned max) {
-	if (nh && nh->nh_ds && nh->nh_ds->ds_usage) {
+	if (nh && nh->nh_ds->ds_usage) {
 		nua_dialog_usage_set_refresh_range(nh->nh_ds->ds_usage, min, max);
 	}
 }