handle missing discription

Author: skarimo

.generator/src/generator/templates/model.j2

@@ -6,7 +6,7 @@ require 'date'
 require 'time'
 
 module {{ module_name }}::{{ version|upper }}
-  # {{ model.description.rstrip()|replace('\n', '\n# ')|indent(2) }}
+  # {{ (model.description or "").rstrip()|replace('\n', '\n# ')|indent(2) }}
 {%- if model.deprecated %}
   #
   # @deprecated This model is deprecated.

.generator/src/generator/templates/model_generic.j2

@@ -16,7 +16,7 @@
      or
       definition.enum is defined #}
 
-    {{ definition.description|block_comment|indent(4) }}
+    {{ (definition.description or "")|block_comment|indent(4) }}
     {%- if has_validation %}
     attr_reader :{{ attr|attribute_name }}
     {%- else %}