Replace len() < 1 with is_empty()

src/main.rs

@@ -145,7 +145,7 @@ fn controllers(config: &Config, filter: bool) -> std::io::Result<Vec<HwMon>> {
 
 fn service(config: Config) -> std::io::Result<()> {
     let mut controllers = controllers(&config, true)?;
-    if controllers.len() < 1 {
+    if controllers.is_empty() {
         return Err(not_found());
     }
     let mut cache = std::collections::HashMap::new();