perf hists browser: Fix up some branch alignment

Those asprintf return checks should be aligned with the other
conditionals, fix it.

Also add {} blocks to further clarify.

Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Borislav Petkov <bp@suse.de>
Cc: David Ahern <dsahern@gmail.com>
Cc: Don Zickus <dzickus@redhat.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Stephane Eranian <eranian@google.com>
echo Link: http://lkml.kernel.org/n/tip-`ranpwd -l 24`@git.kernel.org
Link: http://lkml.kernel.org/n/tip-nqgs07jfphbkw67wja870d3r@git.kernel.org


Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>