[Bug] NullPointException when readHadoopXml

### Search before asking

- [x] I searched in the [issues](https://github.com/apache/paimon/issues) and found nothing similar.

### Paimon version
paimon 1.1
spark 3.2

### Compute Engine

Spark 、 Hive

### Minimal reproduce step

It always happened when my hdfs-site.xml like this:
```

xxxx

```

### What doesn't meet your expectations?

NullPointException when readHadoopXml。

error info:
java.lang.NullPointerException
at org.apache.paimon.utils .HadoopUtils.readHadoopXml(HadoopUtils.java:228)
at org.apache.paimon.utils .HadoopUtils.addHadoopconfIfFound(HadoopUtils .java:175)
....

becasuse hdfs-site.xml like this:
```

xxxx

```

### Anything else?

i have already got down it by modifing org.apache.paimon.utils.readHadoopXml() .
it is very easy.

### Are you willing to submit a PR?

- [x] I'm willing to submit a PR!