fix: fixed error that was allowed in Rust 2015 edition

Author: rand0m-cloud

src/lib.rs

@@ -64,7 +64,7 @@ impl error::Error for Void {
         unreachable(*self)
     }
 
-    fn cause(&self) -> Option<&error::Error> {
+    fn cause(&self) -> Option<&dyn error::Error> {
         unreachable(*self)
     }
 }