update(plugin): make with_last_error() lazy

Only get the error message from the framework if there was
an actual error

Signed-off-by: Grzegorz Nosek <grzegorz.nosek@sysdig.com>

falco_plugin/src/lib.rs

@@ -293,7 +293,6 @@ pub mod async_event {
     /// The event type that can be emitted from async event plugins
     pub use falco_event::events::types::PPME_ASYNCEVENT_E as AsyncEvent;
 
-
     pub use crate::plugin::async_event::async_handler::AsyncHandler;
     pub use crate::plugin::async_event::AsyncEventPlugin;
 

falco_plugin/src/plugin/error/as_result.rs

@@ -35,13 +35,15 @@ where
     type Decorated = anyhow::Result<T>;
 
     fn with_last_error(self, last_error: &LastError) -> Self::Decorated {
-        let Some(msg) = last_error.get() else {
-            return self.map_err(|e| e.into());
-        };
-
         match self {
             Ok(ok) => Ok(ok),
-            Err(_) => self.context(msg),
+            Err(_) => {
+                let Some(msg) = last_error.get() else {
+                    return self.map_err(|e| e.into());
+                };
+
+                self.context(msg)
+            }
         }
     }
 }