Guarantee deletion of tmp file

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

@@ -1520,7 +1520,9 @@ class Core {
                 for (Message imessage : map.keySet()) {
                     EntityMessage message = map.get(imessage);
 
+                    Message icopy;
                     File file = new File(message.getFile(context).getAbsoluteFile() + ".copy");
+                    try {
                         try (OutputStream os = new BufferedOutputStream(new FileOutputStream(file))) {
                             imessage.writeTo(os);
                         }
@@ -1528,7 +1530,6 @@ class Core {
                         Properties props = MessageHelper.getSessionProperties(account.unicode);
                         Session isession = Session.getInstance(props, null);
 
-                    Message icopy;
                         try (InputStream is = new BufferedInputStream(new FileInputStream(file))) {
                             if (duplicate) {
                                 String msgid = EntityMessage.generateMessageId();
@@ -1547,8 +1548,9 @@ class Core {
                             } else
                                 icopy = new MimeMessage(isession, is);
                         }
-
+                    } finally {
                         file.delete();
+                    }
 
                     for (Flags.Flag flag : imessage.getFlags().getSystemFlags())
                         icopy.setFlag(flag, true);