Fix ValidationError initialization to allow default empty errors array

- Updated the ValidationError class to initialize with a default empty array for errors, improving error handling flexibility.
- Enhanced code clarity by separating the error array declaration from the constructor.

Author: eliasjpr

src/active_record/validations.cr

@@ -200,7 +200,9 @@ module CQL
       end
 
       class ValidationError < Exception
-        def initialize(@errors : Array(Error))
+        @errors : Array(Error)
+
+        def initialize(@errors : Array(Error) = [] of Error)
         end
 
         def message