fix heap-use-after-free

Verb::set_tip takes a borrowed string pointer. This line in Effect::check() is
invalid if getErrorReason() returns a temporary:

    _verb.set_tip(Extension::getErrorReason().c_str());

1 files changed, 1 insertions, 1 deletions

diff --git a/src/extension/extension.h b/src/extension/extension.h
index 4a857947e..2ddd8f3f4 100644
--- a/src/extension/extension.h
+++ b/src/extension/extension.h
@@ -143,7 +143,7 @@ public:
     void          deactivate   ();
     bool          deactivated  ();
     void          printFailure (Glib::ustring reason);
-    std::string   getErrorReason() { return _error_reason; };
+    std::string const &getErrorReason() { return _error_reason; };
     Implementation::Implementation * get_imp () { return imp; };
     void          set_execution_env (ExecutionEnv * env) { execution_env = env; };
     ExecutionEnv *get_execution_env () { return execution_env; };