fix: string termination

src/coyote.cpp

@@ -58,8 +58,9 @@ namespace coyote {
 
             size_t hash = std::hash<std::string>{}(
                 iso_dt.value() + std::to_string(yac_time_reduction) + interpolation_stack_yaml);
-            char hash_str[2 * sizeof(hash)];
+            char hash_str[2 * sizeof(hash) + 1];
             std::to_chars(hash_str, hash_str + (2 * sizeof(hash)), hash, 16);
+            hash_str[2 * sizeof(hash)] = 0;
             std::string tgt_field_name = "target:" + source_field + "(" + hash_str + ")";
             int target_field_id        = -1;
             yac_cdef_field(