Do not pass polymorphic exceptions by value.

Author: bbockelm

src/scitokens.cpp

@@ -216,7 +216,7 @@ int validator_validate(Validator validator, SciToken scitoken, char **err_msg) {
 
     try {
         real_validator->verify(*real_scitoken);
-    } catch (std::exception exc) {
+    } catch (std::exception &exc) {
         if (err_msg) {*err_msg = strdup(exc.what());}
         return -1;
     }

src/scitokens_internal.h

@@ -384,7 +384,7 @@ class Enforcer {
         try {
             m_validator.verify(scitoken);
             return true;
-        } catch (std::runtime_error) {
+        } catch (std::runtime_error &) {
             return false;
         }
     }