catch exceptions as const

Signed-off-by: Patrick Williams <patrick@stwcx.xyz>
Change-Id: Id1b5054d3147c39d98309bc11ed7016d6909e2a6
diff --git a/presence/json_parser.cpp b/presence/json_parser.cpp
index bfaedaf..d4f121f 100644
--- a/presence/json_parser.cpp
+++ b/presence/json_parser.cpp
@@ -91,7 +91,7 @@
         }
         log<level::INFO>("Configuration loaded successfully");
     }
-    catch (std::runtime_error& re)
+    catch (const std::runtime_error& re)
     {
         log<level::ERR>("Error loading config, no config changes made",
                         entry("LOAD_ERROR=%s", re.what()));