Make migrations compatible with Mysql 8.

Author: sten

database/migrations/create_filament_flexible_content_block_pages_table.php.stub

@@ -50,7 +50,7 @@ return new class extends Migration
 
             //Content blocks:
             $table->json('content_blocks')
-                ->default('[]'); //Default only works on JSON on MySQL 8 or newer
+                ->nullable();
 
             //Slug:
             $table->json('slug')