Added check for the presence of Content-Type header in the request

services/src/main/java/org/keycloak/services/HttpRequestImpl.java

@@ -59,6 +59,10 @@ public class HttpRequestImpl implements HttpRequest {
         if (delegate == null) {
             return null;
         }
+        MediaType mediaType = getHttpHeaders().getMediaType();
+        if (mediaType.isCompatible(MediaType.valueOf("application/x-www-form-urlencoded"))) {
+            return new MultivaluedHashMap<>();
+        }
         return delegate.getDecodedFormParameters();
     }