config_converter: Fix conversion error to etc/spdk/vhost.conf.in

Just return if the [AIO] section is empty.

Change-Id: I90c42afdca3af7969a1e9d500f92820892857127
Signed-off-by: Shuhei Matsumoto <shuhei.matsumoto.xt@hitachi.com>
Reviewed-on: https://review.gerrithub.io/433199
Tested-by: SPDK CI Jenkins <sys_sgci@intel.com>
Chandler-Test-Pool: SPDK Automated Test System <sys_sgsw@intel.com>
Reviewed-by: Jim Harris <james.r.harris@intel.com>
Reviewed-by: Ben Walker <benjamin.walker@intel.com>
Reviewed-by: Darek Stojaczyk <dariusz.stojaczyk@intel.com>

scripts/config_converter.py

@@ -163,6 +163,8 @@ def get_aio_bdev_json(config, section):
     for option in config.options("AIO"):
         if option == "AIO":
             value = config.get("AIO", option).split("\n")
+    if value is None:
+        return aio_json
     for item in value:
         items = re.findall("\S+", item)
         params = {}