Check error status of command to start playing file.

src/mpvctl/mpvctl.rs

@@ -140,6 +140,12 @@ impl MpvCtl {
         let cmd_result = self.send_command(cmd).await?;
         let result = cmd_result.await?;
         if let serde_json::Value::Object(obj) = result {
+            match obj.get("error") {
+                Some(status) if status == "success" => (),
+                _ => {
+                    return Err("Non-success status".into());
+                }
+            };
             return Ok(());
         } else {
             return Err("Did not get back an object".into());