Remove random empty string from test since it triggers a different exception

Author: s1monw

src/test/java/org/elasticsearch/test/unit/index/mapper/source/DefaultSourceMappingTests.java

@@ -137,7 +137,7 @@ public void testDefaultMappingAndNoMapping() throws Exception {
  assertThat(mapper.type(), equalTo("my_type"));
  assertThat(mapper.sourceMapper().enabled(), equalTo(false));
  try {
- mapper = MapperTestUtils.newParser().parse(null, getRandom().nextBoolean() ? null : "", defaultMapping);
+ mapper = MapperTestUtils.newParser().parse(null, null, defaultMapping);
  assertThat(mapper.type(), equalTo("my_type"));
  assertThat(mapper.sourceMapper().enabled(), equalTo(false));
  assert false;