Don't cast false to empty string in UuidType.

Refs #13523

src/Database/Type/UuidType.php

@@ -32,7 +32,7 @@ class UuidType extends StringType
      */
     public function toDatabase($value, Driver $driver)
     {
-        if ($value === null || $value === '') {
+        if ($value === null || $value === '' || $value === false) {
             return null;
         }
 

tests/TestCase/Database/Type/UuidTypeTest.php

@@ -79,6 +79,9 @@ class UuidTypeTest extends TestCase
 
         $result = $this->type->toDatabase('', $this->driver);
         $this->assertNull($result);
+
+        $result = $this->type->toDatabase(false, $this->driver);
+        $this->assertNull($result);
     }
 
     /**