do not panic on message without event field

intead discard it and try again

src/ipc.rs

@@ -335,15 +335,27 @@ fn try_convert_property(name: &str, id: usize, data: MpvDataType) -> Event {
 }
 
 pub fn listen(instance: &mut Mpv) -> Result<Event, Error> {
+    let mut e;
+    // sometimes we get responses unrelated to events, so we read a new line until we receive one
+    // with an event field
+    let name = loop {
         let mut response = String::new();
         instance.reader.read_line(&mut response).unwrap();
         response = response.trim_end().to_string();
         debug!("Event: {}", response);
 
-    let e = serde_json::from_str::<Value>(&response)
+        e = serde_json::from_str::<Value>(&response)
             .map_err(|why| Error(ErrorCode::JsonParseError(why.to_string())))?;
 
-    if let Value::String(ref name) = e["event"] {
+        match e["event"] {
+            Value::String(ref name) => break name,
+            _ => {
+                // It was not an event - try again
+                debug!("Bad response: {:?}", response)
+            }
+        }
+    };
+
     let event = match name.as_str() {
         "shutdown" => Event::Shutdown,
         "start-file" => Event::StartFile,
@@ -405,9 +417,6 @@ pub fn listen(instance: &mut Mpv) -> Result<Event, Error> {
         _ => Event::Unimplemented,
     };
     Ok(event)
-    } else {
-        unreachable!();
-    }
 }
 
 pub fn listen_raw(instance: &mut Mpv) -> String {