perf top: Fix percent output when no samples collected

size_t perf_top__header_snprintf(struct perf_top *top, char *bf, size_t size)

{

	float samples_per_sec = top->samples / top->delay_secs;

	float ksamples_per_sec = top->kernel_samples / top->delay_secs;

	float esamples_percent = (100.0 * top->exact_samples) / top->samples;

	float samples_per_sec;

	float ksamples_per_sec;

	float esamples_percent;

	struct perf_record_opts *opts = &top->record_opts;

	struct perf_target *target = &opts->target;

	size_t ret = 0;

	if (top->samples) {

		samples_per_sec = top->samples / top->delay_secs;

		ksamples_per_sec = top->kernel_samples / top->delay_secs;

		esamples_percent = (100.0 * top->exact_samples) / top->samples;

	} else {

		samples_per_sec = ksamples_per_sec = esamples_percent = 0.0;

	}

	if (!perf_guest) {

		float ksamples_percent = 0.0;

		if (samples_per_sec)

			ksamples_percent = (100.0 * ksamples_per_sec) /

							samples_per_sec;

		ret = SNPRINTF(bf, size,

			       "   PerfTop:%8.0f irqs/sec  kernel:%4.1f%%"

			       "  exact: %4.1f%% [", samples_per_sec,

			       100.0 - (100.0 * ((samples_per_sec - ksamples_per_sec) /

					samples_per_sec)),

				esamples_percent);

			       ksamples_percent, esamples_percent);

	} else {

		float us_samples_per_sec = top->us_samples / top->delay_secs;

		float guest_kernel_samples_per_sec = top->guest_kernel_samples / top->delay_secs;