compiler: propagate generics in case someone want to have a generic exception

Author: Anaethelion

compiler/src/steps/validate-model.ts

@@ -502,10 +502,10 @@ export default async function validateModel (apiModel: model.Model, restSpec: Ma
       for (const ex of typeDef.exceptions) {
         switch (ex.body.kind) {
           case 'properties':
-            validateProperties(ex.body.properties, new Set<string>(), new Set<string>())
+            validateProperties(ex.body.properties, openGenerics, new Set<string>())
             break
           case 'value':
-            validateValueOf(ex.body.value, new Set<string>())
+            validateValueOf(ex.body.value, openGenerics)
             break
           case 'no_body':
             // Nothing to validate