perf trace: Fix potential NULL pointer dereference found by the smatch tool

Based on the following report from Smatch, fix the potential NULL
pointer dereference check.

  tools/perf/builtin-trace.c:1044
  thread_trace__new() error: we previously assumed 'ttrace' could be
  null (see line 1041).

  tools/perf/builtin-trace.c
  1037 static struct thread_trace *thread_trace__new(void)
  1038 {
  1039         struct thread_trace *ttrace =  zalloc(sizeof(struct thread_trace));
  1040
  1041         if (ttrace)
  1042                 ttrace->files.max = -1;
  1043
  1044         ttrace->syscall_stats = intlist__new(NULL);
               ^^^^^^^^
  1045
  1046         return ttrace;
  1047 }
Signed-off-by: Leo Yan <leo.yan@linaro.org>
Acked-by: Jiri Olsa <jolsa@kernel.org>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Alexey Budankov <alexey.budankov@linux.intel.com>
Cc: Alexios Zavras <alexios.zavras@intel.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Changbin Du <changbin.du@intel.com>
Cc: David S. Miller <davem@davemloft.net>
Cc: Davidlohr Bueso <dave@stgolabs.net>
Cc: Eric Saint-Etienne <eric.saint.etienne@oracle.com>
Cc: Jin Yao <yao.jin@linux.intel.com>
Cc: Konstantin Khlebnikov <khlebnikov@yandex-team.ru>
Cc: Mathieu Poirier <mathieu.poirier@linaro.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Cc: Song Liu <songliubraving@fb.com>
Cc: Suzuki Poulouse <suzuki.poulose@arm.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Thomas Richter <tmricht@linux.ibm.com>
Cc: linux-arm-kernel@lists.infradead.org
Link: http://lkml.kernel.org/r/20190702103420.27540-6-leo.yan@linaro.org
[ Just made it look like other tools/perf constructors, same end result ]
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/builtin-trace.c

@@ -1038,10 +1038,10 @@ static struct thread_trace *thread_trace__new(void)
 {
 	struct thread_trace *ttrace =  zalloc(sizeof(struct thread_trace));
 
-	if (ttrace)
+	if (ttrace) {
 		ttrace->files.max = -1;
-
 		ttrace->syscall_stats = intlist__new(NULL);
+	}
 
 	return ttrace;
 }