Tkinter unable to alloc 71867 bytes

==15145== Invalid write of size 8
             //This is the function doing the incorrect accessing
==15145==    at 0x40168E: split_node_at_letter (in /home/pgolinski/Dokumenty/Programowanie/git/dictionary/trii)
           [... stack trace ...]

                //This is the address you are trying to access
==15145==  Address 0x52237d8 is 8 bytes before a block of size 16 alloc'd
==15145==    at 0x4C29BCF: malloc (in /usr/lib64/valgrind/vgpreload_memcheck-amd64-linux.so)

             //This is the function that alloc'd the 'block of size 16' (calling malloc as shown in the above line)
==15145==    by 0x401063: add_to_trie_word_list (in /home/pgolinski/Dokumenty/Programowanie/git/dictionary/trii)

           [... stack trace ...]

 while ( c == 1 )
   ...

for (;x < i; ++x) {
  printf("%s\n", prefix[x]);
}

while(end > start && string[end - 1] == ' ') --end;