dbus: util: add missing try/catch block

Add try/catch block around ObjectMapper call failures.

Change-Id: I5a2a7a8c1049ea16cebe8b87a509bf5104e432ab
Signed-off-by: Patrick Venture <venture@google.com>
diff --git a/dbus/dbuswrite.hpp b/dbus/dbuswrite.hpp
index 4c5bc29..577013d 100644
--- a/dbus/dbuswrite.hpp
+++ b/dbus/dbuswrite.hpp
@@ -33,6 +33,7 @@
         path(path)
     {
         auto tempBus = sdbusplus::bus::new_default();
+        // getService can except, does it make more sense to use a factory?
         connectionName = helper.getService(tempBus, pwmInterface, path);
     }
 
@@ -53,6 +54,7 @@
         path(path)
     {
         auto tempBus = sdbusplus::bus::new_default();
+        // getService can except, does it make more sense to use a factory?
         connectionName = helper.getService(tempBus, pwmInterface, path);
     }