fix regression from earlier today

src/switch_ivr.c

@@ -263,7 +263,7 @@ SWITCH_DECLARE(switch_status_t) switch_ivr_sleep(switch_core_session_t *session,
 
 				if (args->input_callback) {
 					status = args->input_callback(session, (void *) &dtmf, SWITCH_INPUT_TYPE_DTMF, args->buf, args->buflen);
-				} else {
+				} else if (args->buf) {
 					switch_copy_string((char *) args->buf, (void *) &dtmf, args->buflen);
 					status = SWITCH_STATUS_BREAK;
 				}

src/switch_ivr_play_say.c

@@ -664,7 +664,7 @@ SWITCH_DECLARE(switch_status_t) switch_ivr_record_file(switch_core_session_t *se
 
 				if (args->input_callback) {
 					status = args->input_callback(session, (void *) &dtmf, SWITCH_INPUT_TYPE_DTMF, args->buf, args->buflen);
-				} else {
+				} else if (args->buf) {
 					*((char *) args->buf) = dtmf.digit;
 					status = SWITCH_STATUS_BREAK;
 				}
@@ -911,7 +911,7 @@ SWITCH_DECLARE(switch_status_t) switch_ivr_gentones(switch_core_session_t *sessi
 
 				if (args->input_callback) {
 					status = args->input_callback(session, (void *) &dtmf, SWITCH_INPUT_TYPE_DTMF, args->buf, args->buflen);
-				} else {
+				} else if (args->buf) {
 					*((char *) args->buf) = dtmf.digit;
 					status = SWITCH_STATUS_BREAK;
 				}
@@ -1413,7 +1413,7 @@ SWITCH_DECLARE(switch_status_t) switch_ivr_play_file(switch_core_session_t *sess
 
 					if (args->input_callback) {
 						status = args->input_callback(session, (void *) &dtmf, SWITCH_INPUT_TYPE_DTMF, args->buf, args->buflen);
-					} else {
+					} else if (args->buf) {
 						*((char *) args->buf) = dtmf.digit;
 						status = SWITCH_STATUS_BREAK;
 					}
@@ -2225,7 +2225,7 @@ SWITCH_DECLARE(switch_status_t) switch_ivr_speak_text_handle(switch_core_session
 
 					if (args->input_callback) {
 						status = args->input_callback(session, (void *) &dtmf, SWITCH_INPUT_TYPE_DTMF, args->buf, args->buflen);
-					} else {
+					} else if (args->buf) {
 						*((char *) args->buf) = dtmf.digit;
 						status = SWITCH_STATUS_BREAK;
 					}