DNS: cleanup

app/src/main/java/eu/faircode/email/DnsHelper.java

@@ -673,6 +673,7 @@ public class DnsHelper {
                 ex = new IOException("interrupted");
             }
 
+            try {
                 if (ex == null) {
                     Log.i("DNS Android answer=" + result);
                     return result;
@@ -680,6 +681,10 @@ public class DnsHelper {
                     Log.i(ex);
                     throw ex;
                 }
+            } finally {
+                ex = null;
+                result = null;
+            }
         }
     }