Added temporary checks for Kafka stream types

spring-cloud-function-context/src/main/java/org/springframework/cloud/function/context/catalog/BeanFactoryAwareFunctionRegistry.java

@@ -278,6 +278,13 @@ public class BeanFactoryAwareFunctionRegistry
 							+ "Function available in catalog are: "  + this.getNames(null));
 					return null;
 				}
+				else {
+					Type functionType = FunctionContextUtils.findType(applicationContext.getBeanFactory(), name);
+					if (functionType != null && functionType.toString().contains("org.apache.kafka.streams.")) {
+						logger.debug("Kafka Streams function '" + definition + "' is not supported by spring-cloud-function.");
+						return null;
+					}
+				}
 
 				composedNameBuilder.append(prefix);
 				composedNameBuilder.append(name);

spring-cloud-function-context/src/main/java/org/springframework/cloud/function/context/config/FunctionContextUtils.java

@@ -55,6 +55,9 @@ public abstract class FunctionContextUtils {
 				actualName = name;
 			}
 		}
+		if (definition == null) {
+			return null;
+		}
 
 		Object source = definition.getSource();