TCK: Don't assume every Media Type has a schema

It's valid for a Content object, which represents the content for a
Media Type, not to have a schema, so the filter TCK test should not call
methods on it without checking whether it's present first.

Author: Azquelt

tck/src/main/java/org/eclipse/microprofile/openapi/filter/AirlinesOASFilter.java

@@ -128,7 +128,7 @@ public APIResponse filterAPIResponse(APIResponse apiResponse) {
         if (content != null) {
             if (content.hasMediaType("application/json")) {
                 Schema schema = content.getMediaType("application/json").getSchema();
-                if ("child - id of the new review".equals(schema.getDescription())) {
+                if (schema != null && "child - id of the new review".equals(schema.getDescription())) {
                     schema.setDescription("parent - id of the new review");
                 }
             }