如何修复运行时错误：加载类型为'const char的空指针

Question

我需要编写在哈希表中加载字典的函数。我对错误消息感到困惑：c：37：20运行时错误：加载类型为'const char'的空指针，它在分段错误中运行。

我试图改变加载功能，但仍然没有帮助。并且还试图为哈希表分配内存，因为我认为问题可能在于内存泄漏。

`  // Represents number of buckets in a hash table
#define N 26

// Represents a node in a hash table
typedef struct node

    char word[LENGTH + 1];
    struct node *next;

node;

// Represents a hash table
node *hashtable[N];
// Hashes word to a number between 0 and 25, inclusive, based on its first letter
unsigned int hash(const char *word)

    // Allocates memory for hashtable
    int  *ht = malloc(26*sizeof(int));
    if(!ht)
    
        unload();
        return false;
    
    return tolower(word[0]) - 'a';  // this is error line 37:20


// Loads dictionary into memory, returning true if successful else false
bool load(const char *dictionary)


    // Initialize hash table
    for (int i = 0; i < N; i++)
    
        hashtable[i] = NULL;
    

    // Open dictionary
    FILE *file = fopen(dictionary, "r");
    if (file == NULL)
    
        unload();
        return false;
    

    // Buffer for a word
    char word[LENGTH + 1];

    // Insert words into hash table
    while (fscanf(file, "%s", word) != EOF)
    

        for (int i = 0; i < N; i++ )
        
            // Allocate memory for node for each new word
            node *new_node = malloc(sizeof(node));
            if (!new_node)
            
                unload();
                return false;
            
            // Copies word into node
            strcpy(new_node->word, word);
            new_node->next = NULL;
            // Hashes word
            hash(new_node->word);
            // Inserts word into linked list
            if(hashtable[i] == 0)
            
                hashtable[i] = new_node;

            
            else if(hashtable[i] == new_node)
            
               new_node->next = hashtable[i];
               hashtable[i] = new_node;
            
        
    

    // Close dictionary
    fclose(file);

    // Indicate success
    return true;

加载字典时，函数加载应返回true。但是我得到了分段错误。这是否意味着我没有从加载功能得到正确的输出？