mailcap: don't drop File before opening it

Created temporary file was incorrectly set to be deleted on Drop, but
this is not what we want to do when spawning an external command and pass
the file as the argument.

Fixes: #548 ("mailcap handling")

Resolves: <https://git.meli-email.org/meli/meli/issues/548>
Signed-off-by: Manos Pitsidianakis <manos@pitsidianak.is>

meli/src/mailcap.rs

@@ -167,14 +167,14 @@ impl MailcapEntry {
                     .map(|arg| match *arg {
                         "%s" => {
                             needs_stdin = false;
-                            let _f = File::create_temp_file(
+                            let file = File::create_temp_file(
                                 &a.decode(Default::default()),
                                 None,
                                 None,
                                 None,
-                                true,
+                                false,
                             )?;
-                            let p = _f.path().display().to_string();
+                            let p = file.path().display().to_string();
                             Ok(p)
                         }
                         "%t" => Ok(a.content_type().to_string()),