Filter out null fixed option from generated migrations (#1048)

When generating migrations, the 'fixed' option could be set to null for
binary columns, which causes an error when running the migration because
Column::setFixed() expects a bool, not null.

Fixes #1046

Author: dereuromark

src/View/Helper/MigrationHelper.php

@@ -401,6 +401,10 @@ public function getColumnOption(array $options): array
         if (empty($columnOptions['collate'])) {
             unset($columnOptions['collate']);
         }
+        // isset() returns false for null values, so this handles both missing and null cases
+        if (!isset($columnOptions['fixed'])) {
+            unset($columnOptions['fixed']);
+        }
 
         // currently only MySQL supports the signed option
         $driver = $connection->getDriver();