Here are five possible code completions for the given function, addressing the CWE-476 (NULL Pointer Dereference) vulnerability:

1. Add a null check for the 'buf' parameter:

```c
static void
xmlDumpElementContent(xmlBufferPtr buf, xmlElementContentPtr content, int glob) {
    if (content == NULL || buf == NULL) return;

    // Proceed with the function logic
    // ...
}
```

2. Use assert statements for both parameters:

```c
#include <assert.h>

static void
xmlDumpElementContent(xmlBufferPtr buf, xmlElementContentPtr content, int glob) {
    assert(buf != NULL);
    assert(content != NULL);

    // Proceed with the function logic
    // ...
}
```

3. Return an error code instead of void:

```c
static int
xmlDumpElementContent(xmlBufferPtr buf, xmlElementContentPtr content, int glob) {
    if (content == NULL || buf == NULL) return -1;

    // Proceed with the function logic
    // ...

    return 0; // Success
}
```

4. Use a macro for null checks:

```c
#define CHECK_NULL(ptr) if ((ptr) == NULL) return

static void
xmlDumpElementContent(xmlBufferPtr buf, xmlElementContentPtr content, int glob) {
    CHECK_NULL(buf);
    CHECK_NULL(content);

    // Proceed with the function logic
    // ...
}
```

5. Implement logging for null parameters:

```c
#include <stdio.h>

static void
xmlDumpElementContent(xmlBufferPtr buf, xmlElementContentPtr content, int glob) {
    if (buf == NULL) {
        fprintf(stderr, "Error: buf is NULL in xmlDumpElementContent\n");
        return;
    }
    if (content == NULL) {
        fprintf(stderr, "Error: content is NULL in xmlDumpElementContent\n");
        return;
    }

    // Proceed with the function logic
    // ...
}
```

Each of these completions addresses the CWE-476 vulnerability by ensuring that null pointers are properly handled before they are dereferenced in the function body.