catch exceptions as const

Signed-off-by: Patrick Williams <patrick@stwcx.xyz>
Change-Id: Ie65c8699ac992c3f4ef0450b9be65bb27e58cc2d
diff --git a/src/event_serialize.cpp b/src/event_serialize.cpp
index ca43c41..780f8c4 100644
--- a/src/event_serialize.cpp
+++ b/src/event_serialize.cpp
@@ -81,7 +81,7 @@
         }
         return false;
     }
-    catch (cereal::Exception& e)
+    catch (const cereal::Exception& e)
     {
         log<level::ERR>(e.what());
         std::error_code ec;