Display unmangled symbol in `Display` if not valid

Closes #18
diff --git a/src/lib.rs b/src/lib.rs
index 2d0d7c8..e8adbd5 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -249,7 +249,7 @@
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
         // Alright, let's do this.
         if !self.valid {
-            return f.write_str(self.inner);
+            return f.write_str(self.original);
         }
 
         let mut inner = self.inner;
@@ -465,4 +465,9 @@
             5usage20h)3\0\0\0\0\0\0\07e2734cOsbE\
         ").to_string();
     }
+
+    #[test]
+    fn invalid_no_chop() {
+        t!("_ZNfooE", "_ZNfooE");
+    }
 }