txt-dump: fix encoding of unprintable characters

src/libknot/rrset-dump.c

@@ -549,9 +549,9 @@ static void wire_text_to_str(rrset_dump_params_t *p)
 
 	// Loop over all characters.
 	for (size_t i = 0; i < in_len; i++) {
-		char ch = (char)(p->in)[i];
+		uint8_t ch = p->in[i];
 
-		if (isprint((unsigned char)(ch)) != 0) {
+		if (isprint(ch) != 0) {
 			// For special character print leading slash.
 			if (ch == '\\' || ch == '"') {
 				dump_string(p, "\\");