cJSON_ArrayForEach: Fix handling of NULL pointers

cJSON.h

@@ -176,7 +176,7 @@ extern double cJSON_SetNumberHelper(cJSON *object, double number);
 #define cJSON_SetNumberValue(object, number) ((object != NULL) ? cJSON_SetNumberHelper(object, (double)number) : (number))
 
 /* Macro for iterating over an array */
-#define cJSON_ArrayForEach(pos, head) for(pos = (head)->child; pos != NULL; pos = pos->next)
+#define cJSON_ArrayForEach(element, array) for(element = (array != NULL) ? (array)->child : NULL; element != NULL; element = element->next)
 
 #ifdef __cplusplus
 }