condition: return (Condition*) NULL from condition_free()

Follow our usual coding style.

src/shared/condition.c

@@ -73,11 +73,11 @@ Condition* condition_new(ConditionType type, const char *parameter, bool trigger
         return c;
 }
 
-void condition_free(Condition *c) {
+Condition* condition_free(Condition *c) {
         assert(c);
 
         free(c->parameter);
-        free(c);
+        return mfree(c);
 }
 
 Condition* condition_free_list_type(Condition *head, ConditionType type) {

src/shared/condition.h

@@ -67,7 +67,7 @@ typedef struct Condition {
 } Condition;
 
 Condition* condition_new(ConditionType type, const char *parameter, bool trigger, bool negate);
-void condition_free(Condition *c);
+Condition* condition_free(Condition *c);
 Condition* condition_free_list_type(Condition *first, ConditionType type);
 static inline Condition* condition_free_list(Condition *first) {
         return condition_free_list_type(first, _CONDITION_TYPE_INVALID);