Return correct message type.

Fix #911

CHANGELOG.md

@@ -9,6 +9,7 @@ Exclamation symbols (:exclamation:) note something of importance e.g. breaking c
 ### Deprecated
 ### Removed
 ### Fixed
+- Return correct message type.
 ### Security
 
 ## [0.55.0] - 2018-12-20

src/Entities/Message.php

@@ -313,7 +313,7 @@ class Message extends Entity
 
         $is_command = strlen($this->getCommand()) > 0;
         foreach ($types as $type) {
-            if ($this->getProperty($type)) {
+            if ($this->getProperty($type) !== null) {
                 if ($is_command && $type === 'text') {
                     return 'command';
                 }