Fix -Wswitch in example/jsonfindptrs
diff --git a/example/jsonfindptrs/jsonfindptrs.cc b/example/jsonfindptrs/jsonfindptrs.cc
index 0d6930d..7996b09 100644
--- a/example/jsonfindptrs/jsonfindptrs.cc
+++ b/example/jsonfindptrs/jsonfindptrs.cc
@@ -420,8 +420,9 @@
           return "";
         }
         return "main: internal error: non-string map key";
+      default:
+        return "main: internal error: non-container stack entry";
     }
-    return "main: internal error: non-container stack entry";
   }
 
   std::string AppendNull() override {