perf trace: Fix IS_ERR() vs NULL check bug

The alloc_syscall_stats() function always returns an error pointer
(ERR_PTR) on failure.

So replace NULL check with IS_ERR() check after calling
alloc_syscall_stats() function.

Fixes: fc00897c8a3f7f57 ("perf trace: Add --summary-mode option")
Reviewed-by: Ian Rogers <[e-mail]>
Signed-off-by: Fushuai Wang <[e-mail]>
Cc: Adrian Hunter <[e-mail]>
Cc: Alexander Shishkin <[e-mail]>
Cc: Ingo Molnar <[e-mail]>
Cc: Jiri Olsa <[e-mail]>
Cc: Kan Liang <[e-mail]>
Cc: Mark Rutland <[e-mail]>
Cc: Namhyung Kim <[e-mail]>
Cc: Peter Zijlstra <[e-mail]>
Signed-off-by: Arnaldo Carvalho de Melo <[e-mail]>

tools/perf/builtin-trace.c

···
 
 	if (trace->summary_mode == SUMMARY__BY_TOTAL && !trace->summary_bpf) {
 		trace->syscall_stats = alloc_syscall_stats();
-		if (trace->syscall_stats == NULL)
+		if (IS_ERR(trace->syscall_stats))
 			goto out_delete_evlist;
 	}
 
···
 
 	if (trace->summary_mode == SUMMARY__BY_TOTAL) {
 		trace->syscall_stats = alloc_syscall_stats();
-		if (trace->syscall_stats == NULL)
+		if (IS_ERR(trace->syscall_stats))
 			goto out;
 	}