LLVM scan-build warnings

[jkvis]

We need to understand the following warnings:

src/trie.c:137:9: warning: Potential leak of memory pointed to by 'split'
        free(node);
        ^~~~
src/trie.c:366:23: warning: Attempt to free released memory
    void* const ret = realloc(*key, len + node->len);
                      ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
src/trie.c:383:23: warning: Attempt to free released memory
    void* const ret = realloc(*key, len + 1);
                      ^~~~~~~~~~~~~~~~~~~~~~