Disable empty passphrase for S/MIME CSRs

GnuPG and GPGME currently don't support to set a passphrase
callback for S/MIME. So we hide it to avoid an "not implemented"
error.

src/newcertificatewizard/newcertificatewizard.cpp

@@ -816,6 +816,11 @@ public:
         const auto entry = conf->entry(QStringLiteral("gpg-agent"),
                                    QStringLiteral("Passphrase policy"),
                                    QStringLiteral("enforce-passphrase-constraints"));
+        if (!pgp()) {
+            // GnuPG / GPGME as of 2.2.27 do not support
+            // pinentry mode and passphrase setting for S/MIME
+            ui.withPassCB->setVisible(false);
+        }
         if (entry && entry->boolValue()) {
             qCDebug(KLEOPATRA_LOG) << "Disabling passphrace cb because of agent config.";
             ui.withPassCB->setEnabled(false);
@@ -892,7 +897,7 @@ private:
         if (!j) {
             return;
         }
-        if (!protectedKey ()) {
+        if (!protectedKey() && pgp()) {
             auto ctx = QGpgME::Job::context(j);
             ctx->setPassphraseProvider(&mEmptyPWProvider);
             ctx->setPinentryMode(Context::PinentryLoopback);