ENC: fix possible memory error

LZ4_compress might add a null-byte, so we have to account for that.

src/ntru_encrypt.c

@@ -63,7 +63,7 @@ get_compressed_str(const string *str)
 	if (!str)
 		NTRU_ABORT_DEBUG("Unexpected NULL parameters");
 
-	max_output_size = str->len;
+	max_output_size = str->len + 1;
 	compressed_str = ntru_malloc(sizeof(string));
 	compressed_str->ptr = ntru_malloc(
 			sizeof(char) * max_output_size);