PHP 8.1 deprecations fix

Author: maxgorovenko

src/Entities/Message.php

@@ -158,7 +158,7 @@ public function getCommand(): ?string
         }
 
         $full_command = $this->getFullCommand();
-        if (strpos($full_command, '/') !== 0) {
+        if (!is_string($full_command) || strpos($full_command, '/') !== 0) {
             return null;
         }
         $full_command = substr($full_command, 1);
@@ -261,7 +261,7 @@ public function getType(): string
             'reply_markup',
         ];
 
-        $is_command = strlen($this->getCommand()) > 0;
+        $is_command = is_string($command = $this->getCommand()) && strlen($command) > 0;
         foreach ($types as $type) {
             if ($this->getProperty($type) !== null) {
                 if ($is_command && $type === 'text') {