fixed returns

WatcherAgent/src/hardware/memory.rs

@@ -1,3 +1,5 @@
+use std::error::Error;
+
 use anyhow::Result;
 use sysinfo::System;
 
@@ -19,7 +21,7 @@ pub async fn get_memory_info() -> Result<MemoryInfo> {
     })
 }
 
-pub fn _get_memory_usage(sys: &mut System) -> f64 {
+pub fn _get_memory_usage(sys: &mut System) -> Result<f64, Box<dyn Error>> {
     sys.refresh_memory();
-    (sys.used_memory() as f64 / sys.total_memory() as f64) * 100.0
+    Ok((sys.used_memory() as f64 / sys.total_memory() as f64) * 100.0)
 }