Fix mosquitto_{pub|sub}_topic_check() function returns.

The would not return MOSQ_ERR_INVAL on topic == NULL.

ChangeLog.txt

@@ -8,10 +8,15 @@ Broker:
 - Give compile time warning if libwebsockets compiled without external poll
   support. Closes #2060.
 
+Client library:
+- Fix mosquitto_{pub|sub}_topic_check() functions not returning MOSQ_ERR_INVAL
+  on topic == NULL.
+
 Clients:
 - Fix possible loss of data in `mosquitto_pub -l` when sending multiple long
   lines. Closes #2078.
 
+
 2.0.7 - 2021-02-04
 ==================
 

lib/util_topic.c

@@ -54,6 +54,11 @@ int mosquitto_pub_topic_check(const char *str)
 #ifdef WITH_BROKER
 	int hier_count = 0;
 #endif
+
+	if(str == NULL){
+		return MOSQ_ERR_INVAL;
+	}
+
 	while(str && str[0]){
 		if(str[0] == '+' || str[0] == '#'){
 			return MOSQ_ERR_INVAL;
@@ -81,7 +86,9 @@ int mosquitto_pub_topic_check2(const char *str, size_t len)
 	int hier_count = 0;
 #endif
 
-	if(len > 65535) return MOSQ_ERR_INVAL;
+	if(str == NULL || len > 65535){
+		return MOSQ_ERR_INVAL;
+	}
 
 	for(i=0; i<len; i++){
 		if(str[i] == '+' || str[i] == '#'){
@@ -115,7 +122,11 @@ int mosquitto_sub_topic_check(const char *str)
 	int hier_count = 0;
 #endif
 
-	while(str && str[0]){
+	if(str == NULL){
+		return MOSQ_ERR_INVAL;
+	}
+
+	while(str[0]){
 		if(str[0] == '+'){
 			if((c != '\0' && c != '/') || (str[1] != '\0' && str[1] != '/')){
 				return MOSQ_ERR_INVAL;
@@ -150,7 +161,9 @@ int mosquitto_sub_topic_check2(const char *str, size_t len)
 	int hier_count = 0;
 #endif
 
-	if(len > 65535) return MOSQ_ERR_INVAL;
+	if(str == NULL || len > 65535){
+		return MOSQ_ERR_INVAL;
+	}
 
 	for(i=0; i<len; i++){
 		if(str[i] == '+'){