Update container free methods (#58)

include/vtype.h

@@ -144,7 +144,7 @@ inline size_t array_size   (const vtype_array*  x) { return x->size; }
 inline size_t dict_size    (const vtype_dict*   x) { return x->size; }
 inline size_t dict_capacity(const vtype_dict*   x) { return x->capacity; }
 inline size_t string_nmemb (const vtype_string* x) { return (x->buffer) ? libcdsb_strlen(x->buffer) : 0; }
-inline void   string_free  (      vtype_string* x) { libcdsb_free(x->buffer); x->buffer = 0; }
+inline void   string_free  (      vtype_string* x) { if (x) { libcdsb_free(x->buffer); x->buffer = 0; } }
 
 inline vtype_string string_copy(const vtype_string* s) {
     vtype_string x = { .buffer = libcdsb_strdup(s->buffer) };

src/array/memory.c

@@ -5,6 +5,8 @@
 #include "../__internal/assert.h"
 
 void array_free(arr_t* x) {
+    if (is_null(x)) return;
+
     if (x->size && x->type >= VTYPE_STRING) {
         void* p = x->mem;
 

src/dict/memory.c

@@ -4,6 +4,7 @@
 #include "include.h"
 
 void dict_free(dict_t* x) {
+    if (is_null(x)) return;
 
     while (x->capacity--) {
         while (!is_null(x->nodes[x->capacity])) {

src/list/memory.c

@@ -7,6 +7,8 @@ void list_free(list_t* x) {
     lnode_t* c;
     lnode_t* next;
 
+    if (is_null(x)) return;
+
     c = x->first;
 
     while (!is_null(c)) {

src/map/memory.c

@@ -12,6 +12,8 @@ void map_init(map_t* x, vtype t) {
 void map_free(map_t* x) {
     mnode_t *t, *c;
 
+    if (is_null(x)) return;
+
     c = x->root;
 
     while (!mnode_is_empty(x->root)) {

src/set/memory.c

@@ -12,6 +12,8 @@ void vset_init(set_t* x, vtype t) {
 void vset_free(set_t* x) {
     rbnode_t *t, *c;
 
+    if (is_null(x)) return;
+
     c = x->root;
 
     while (!rbnode_is_empty(x->root)) {