intn: intn_from_integer_bytes: set sign when sign != NULL

When sign parameter is non-null, always set it to a known value.
This avoids annoying bugs.

Signed-off-by: Davide Bettio <[email protected]>

Author: bettio

src/libAtomVM/intn.c

@@ -1182,6 +1182,8 @@ int intn_from_integer_bytes(const uint8_t in[], size_t in_size, intn_from_intege
             sign = IntNNegativeInteger;
         }
         *out_sign = sign;
+    } else if (out_sign) {
+        *out_sign = IntNPositiveInteger;
     }
 
     memset(out, filler, INTN_MAX_RES_LEN * sizeof(intn_digit_t));