fixed NPE in ArangoCursor (issue #112)

Author: mpv1989

ChangeLog

@@ -5,6 +5,7 @@ v4.1.11 (2017-03-xx)
 * fixed exception handling in Connection (issue #110)
 * added connection pooling (issue #103)
 * extracted VelocyPack implementation to https://github.com/arangodb/java-velocypack
+* fixed NPE in ArangoCursor (issue #112)
 
 v4.1.10 (2017-02-22)
 ---------------------------

src/main/java/com/arangodb/ArangoCursor.java

@@ -97,7 +97,9 @@ public boolean isCached() {
 
 	@Override
 	public void close() throws IOException {
-		execute.close(id);
+		if (id != null) {
+			execute.close(id);
+		}
 	}
 
 	@Override

src/test/java/com/arangodb/ArangoDatabaseTest.java

@@ -534,6 +534,18 @@ public void queryClose() throws IOException {
 
 	}
 
+	@Test
+	public void queryNoResults() throws IOException {
+		try {
+			db.createCollection(COLLECTION_NAME);
+			final ArangoCursor<BaseDocument> cursor = db.query("FOR i IN @@col RETURN i",
+				new MapBuilder().put("@col", COLLECTION_NAME).get(), null, BaseDocument.class);
+			cursor.close();
+		} finally {
+			db.collection(COLLECTION_NAME).drop();
+		}
+	}
+
 	@Test
 	public void explainQuery() {
 		final AqlExecutionExplainEntity explain = arangoDB.db().explainQuery("for i in _apps return i", null, null);