[PATCH v1 4/8] perf stat: Drop metric-unit if unit is NULL

[Ian Rogers]

Avoid cases like:
```
$ perf stat -a -M topdownl1 -j -I 1000
...
{"interval" : 11.127757275, "counter-value" : "85715898.000000", "unit" : "", "event" : "IDQ.MITE_UOPS", "event-runtime" : 988376123, "pcnt-running" : 100.00, "metric-value" : "0.000000", "metric-unit" : "(null)"}
...
```

Signed-off-by: Ian Rogers <irogers@xxxxxxxxxx>
---
 tools/perf/util/stat-display.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/tools/perf/util/stat-display.c b/tools/perf/util/stat-display.c
index e392ee5efb45..9b65968e37d1 100644
--- a/tools/perf/util/stat-display.c
+++ b/tools/perf/util/stat-display.c
@@ -470,8 +470,9 @@ static void print_metric_json(struct perf_stat_config *config __maybe_unused,
 	struct outstate *os = ctx;
 	FILE *out = os->fh;
 
-	fprintf(out, "\"metric-value\" : \"%f\", ", val);
-	fprintf(out, "\"metric-unit\" : \"%s\"", unit);
+	fprintf(out, "\"metric-value\" : \"%f\"", val);
+	if (unit)
+		fprintf(out, ", \"metric-unit\" : \"%s\"", unit);
 	if (!config->metric_only)
 		fprintf(out, "}");
 }
-- 
2.47.0.rc0.187.ge670bccf7e-goog