FALSE NEGATIVE: NULLPTR_DEREFERENCE misses a local null in a FileChannel catch path

Hi, I found a false negative in Infer 1.3.0 when the catch block initializes object to null and immediately dereferences it.

**Affected checker**

`Infer NULLPTR_DEREFERENCE`

**Minimal reproducer**

```java
import java.io.IOException;
import java.nio.channels.FileChannel;

class InferNullFileChannelCatch {
String test(FileChannel channel) {
try {
channel.tryLock();
return "";
} catch (IOException exception) {
Object object = null;
return object.toString();
}
}
}
```

**Reproduction command**

```bash
infer --version
infer run --pulse --enable-issue-type NULLPTR_DEREFERENCE -- javac infer-nullptr-fn-filechannel-catch.java
```

**Current behavior**

Infer completes successfully but produces no `NULLPTR_DEREFERENCE` finding. The same catch body is reported when `FileChannel.tryLock()` is replaced with `InputStream.read()`.

**Expected behavior**

Infer should report `NULLPTR_DEREFERENCE` at line 11 because the catch block initializes object to null and immediately dereferences it.