Do not rely on existance of Message-ID header.

There may be mails without any Message-ID header and those mails trigger
a segfault.

messagecore/src/autocrypt/autocryptutils.cpp

@@ -66,10 +66,15 @@ void MessageCore::processAutocryptfromMail(const HeaderMixupNodeHelper &mixup)
 {
     auto storage = AutocryptStorage::self();
 
+    QByteArray messageid = "<NO Message-ID header>";
+    if  (mixup.mailHeaderAsBase("Message-ID")) {
+        messageid = mixup.mailHeaderAsBase("Message-ID")->as7BitString(false);
+    }
+
     const auto fromAddr = mixup.mailHeaderAsAddressList("from");
     if (fromAddr->addresses().size() != 1) {
-        qInfo(AUTOCRYPT_LOG) << "Don't update Autocrypt storage, because we have multiple From addresses found in "
-                             << mixup.mailHeaderAsBase("Message-ID")->as7BitString(false);
+        qInfo(AUTOCRYPT_LOG) << "Don't update Autocrypt storage, none or multiple From headers found in "
+                             << messageid;
         return;
     }
 
@@ -109,17 +114,17 @@ void MessageCore::processAutocryptfromMail(const HeaderMixupNodeHelper &mixup)
             auto recipient = storage->addRecipient(params.value("addr"));
             recipient->updateFromMessage(mixup, header);
             qInfo(AUTOCRYPT_LOG) << "Update Autocrypt information for " << recipient->addr() << " from "
-                                 << mixup.mailHeaderAsBase("Message-ID")->as7BitString(false);
+                                 << messageid;
         } else {
             qInfo(AUTOCRYPT_LOG) << "Don't update Autocrypt storage, because we have multiple valid Autocrypt headers found in "
-                                 << mixup.mailHeaderAsBase("Message-ID")->as7BitString(false);
+                                 << messageid;
         }
     } else {
         auto recipient = storage->getRecipient(fromAddr->addresses().value(0));
         if (recipient) {
             recipient->updateFromMessage(mixup, nullptr);
             qInfo(AUTOCRYPT_LOG) << "Update Autocrypt information for " << recipient->addr() << " from "
-                                 << mixup.mailHeaderAsBase("Message-ID")->as7BitString(false);
+                                 << messageid;
         }
     }
 
@@ -137,7 +142,7 @@ void MessageCore::processAutocryptfromMail(const HeaderMixupNodeHelper &mixup)
                 auto recipient = storage->addRecipient(params.value("addr"));
                 recipient->updateFromGossip(mixup, header);
                 qInfo(AUTOCRYPT_LOG) << "Update Autocrypt Gossip information for" << recipient->addr() << " from "
-                                     << mixup.mailHeaderAsBase("Message-ID")->as7BitString(false);
+                                     << messageid;
             }
         }
     }