chassis: fix clang-tidy warning

```
/data0/jenkins/workspace/ci-repository/openbmc/bmcweb/redfish-core/lib/chassis.hpp:130:13: error: loop will run at most once (loop increment never executed) [clang-diagnostic-unreachable-code-loop-increment,-warnings-as-errors]
            for (const auto& service : object.second)
```

Signed-off-by: Patrick Williams <patrick@stwcx.xyz>
Change-Id: I3d7743115ec31d6f704a857f3e878fa1b7728a60
diff --git a/redfish-core/lib/chassis.hpp b/redfish-core/lib/chassis.hpp
index 31b38c3..c64d27c 100644
--- a/redfish-core/lib/chassis.hpp
+++ b/redfish-core/lib/chassis.hpp
@@ -127,8 +127,9 @@
         // Iterate over all retrieved ObjectPaths.
         for (const auto& object : subtree)
         {
-            for (const auto& service : object.second)
+            if (!object.second.empty())
             {
+                const auto service = object.second.front();
                 getIntrusionByService(aResp, service.first, object.first);
                 return;
             }