Fixes issue #2087 - No mime_type on nil message (no message body) / email will not be processed.

app/models/channel/email_parser.rb

@@ -504,7 +504,7 @@ process unprocessable_mails (tmp/unprocessable_mail/*.eml) again
   def message_body_hash(mail)
     message = [mail.html_part, mail.text_part, mail].find { |m| m&.body.present? }
 
-    if message.mime_type.nil? || message.mime_type.match?(%r{^text/(plain|html)$})
+    if message.present? && (message.mime_type.nil? || message.mime_type.match?(%r{^text/(plain|html)$}))
       content_type = message.mime_type || 'text/plain'
       body = body_text(message, strict_html: content_type.eql?('text/html'))
     end

test/data/mail/mail067.box

@@ -0,0 +1,19 @@
+Return-Path: <info@example.de>
+X-Original-To: info@example.de
+Delivered-To: m032b9f7@dd38536.example.com
+Received: from dd38536.example.com (dd0801.example.com [1.1.1.1])
+	by dd38536.example.com (Postfix) with ESMTPSA id 343463D42403
+	for <info@example.de>; Wed,  4 Jul 2018 10:02:32 +0200 (CEST)
+MIME-Version: 1.0
+Content-Type: text/plain; charset=ISO-8859-1
+Content-Transfer-Encoding: 8bit
+X-SenderIP: 1.1.1.1
+User-Agent: ALL-INKL Webmail 2.11
+Subject: Testmail - Alias in info@example.de Gruppe
+From: "Bob Smith | deal" <info@example.de>
+To: info@example.de
+Message-Id: <20180704080232.343463D42403@dd38536.example.com>
+Date: Wed,  4 Jul 2018 10:02:32 +0200 (CEST)
+X-KasLoop: m032b9f7
+
+ 

test/unit/email_process_test.rb

@@ -2804,6 +2804,33 @@ Some Text',
           },
         },
       },
+      {
+        data: File.read(Rails.root.join('test', 'data', 'mail', 'mail067.box')),
+        success: true,
+        result: {
+          0 => {
+            priority: '2 normal',
+            title: 'Testmail - Alias in info@example.de Gruppe',
+          },
+          1 => {
+            from: 'Bob Smith | deal <info@example.de>',
+            sender: 'Customer',
+            type: 'email',
+            subject: 'Testmail - Alias in info@example.de Gruppe',
+            body: 'no visible content',
+          },
+        },
+        verify: {
+          users: [
+            {
+              firstname: 'Bob',
+              lastname: 'Smith | deal',
+              fullname: 'Bob Smith | deal',
+              email: 'info@example.de',
+            },
+          ],
+        },
+      },
     ]
     assert_process(files)
   end