tools: Fix potential null-deref with result of strtok_r

Return value of a function 'strtok_r' is dereferenced at kwbimage.c:1655
without checking for NULL, but it is usually checked for this function.

Signed-off-by: Maks Mishin <maks.mishinFZ@gmail.com>

tools/kwbimage.c

@@ -1653,6 +1653,12 @@ static int image_create_config_parse_oneline(char *line,
 	char *unknown_msg = "Ignoring unknown line '%s'\n";
 
 	keyword = strtok_r(line, delimiters, &saveptr);
+
+	if (!keyword) {
+		fprintf(stderr, "Parameter missing in line '%s'\n", line);
+		return -1;
+	}
+
 	keyword_id = recognize_keyword(keyword);
 
 	if (!keyword_id) {