[REFACTOR] [Hacker Rank] Warmup: Time Conversion solved ✅. Trying to solve sonarcloud warnings.

Author: Gonzalo Diaz

src/lib/exercises/src/hackerrank/warmup/time_conversion.c

@@ -12,9 +12,9 @@
 
 char *HACKERRANK_WARMUP_getFirst(const char *s, unsigned long n) {
   char dest[HACKERRANK_WARMUP_MAX_STRING_SIZE + 1];
-  dest[sizeof dest - 1] = 0;
+  dest[sizeof dest - 1] = NULL;
   strncpy(dest, s, sizeof dest);
-  if (dest[sizeof dest - 1] != 0) {
+  if (dest[sizeof dest - 1] != NULL) {
     return NULL; // Handle error
   }
   size_t s_len = strlen(s);