DATAJDBC-162 - Prevent NPE for missing PropertyPath in DbActionExecutionException.

src/main/java/org/springframework/data/jdbc/core/conversion/DbActionExecutionException.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2017 the original author or authors.
+ * Copyright 2018 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -28,7 +28,7 @@ public class DbActionExecutionException extends RuntimeException {
 						action.getClass().getSimpleName(), //
 						action.getEntity(), //
 						action.getEntityType(), //
-						action.getPropertyPath().toDotPath() //
+						action.getPropertyPath() == null ? "" : action.getPropertyPath().toDotPath() //
 				), //
 				cause);
 	}