catch exceptions as const

Signed-off-by: Patrick Williams <patrick@stwcx.xyz>
Change-Id: Id1b5054d3147c39d98309bc11ed7016d6909e2a6
diff --git a/presence/tach.cpp b/presence/tach.cpp
index 7304676..4c2dc14 100644
--- a/presence/tach.cpp
+++ b/presence/tach.cpp
@@ -69,7 +69,7 @@
             std::get<double>(s) = util::SDBusPlus::getProperty<double>(
                 tachPath, tachIface, tachProperty);
         }
-        catch (std::exception&)
+        catch (const std::exception&)
         {
             // Assume not spinning.