cpuset_parse: make a check for an empty string in cpu_in_cpuset()

Fixes: Coverity 382195
Signed-off-by: Alexander Mikhalitsyn <aleksandr.mikhalitsyn@canonical.com>

src/cpuset_parse.c

@@ -39,6 +39,9 @@ static int cpuset_getrange(const char *c, int *a, int *b)
  */
 bool cpu_in_cpuset(int cpu, const char *cpuset)
 {
+	if (!strlen(cpuset))
+		return false;
+
 	for (const char *c = cpuset; c; c = cpuset_nexttok(c)) {
 		int a, b, ret;