aomenc: Throw error if config file parsing fails

Earlier, config file reading/parsing errors were silently being ignored.

Change-Id: I3d86ac440fd3f7a238461dacc69abb32d0af474a
diff --git a/apps/aomenc.c b/apps/aomenc.c
index a69eb16..89b87c7 100644
--- a/apps/aomenc.c
+++ b/apps/aomenc.c
@@ -1207,7 +1207,9 @@
 
     if (arg_match(&arg, &use_cfg, argi)) {
       if (cfg_included) continue;
-      parse_cfg(arg.val, &global->encoder_config);
+      if (parse_cfg(arg.val, &global->encoder_config)) {
+        die("Reading / parsing error for config file: %s\n", arg.val);
+      }
       cfg_included = 1;
       continue;
     }