### Godot version

4.2.x master [5df98679672c12d96b4ac4d96ee17f1559207401]

### System information

Linux - GCC g++ 9.4.0 - Ubuntu 20.04 LTS

### Issue description

I somehow managed to get my Windows system into a broken state were the driver reports 145 extensions, but extension `#144` is an empty string.

Therefore Godot will crash while initializing Vulkan and looking for requested device extensions.

### Steps to reproduce

Execute the following code:

```cpp
HashMap<CharString, bool> requested_device_extensions;

CharString extension_name("");
CharString extension_name2("Hello");

requested_device_extensions.insert("HashMap must not be empty", true);

if (requested_device_extensions.has(extension_name2))
	printf("Has Hello\n");
if (requested_device_extensions.has(extension_name))
	printf("Has <empty>\n");
```

It will crash before <empty>. Callstack:

                                                                                                                                                                                                
```                                                                                                                                                                                                
1 hash_djb2                                                                                                                                                   hashfuncs.h        64   0x4a135d6 
2 HashMapHasherDefault::hash                                                                                                                                  hashfuncs.h        313  0x4a1decd 
3 HashMap<CharString, bool, HashMapHasherDefault, HashMapComparatorDefault<CharString>, DefaultTypedAllocator<HashMapElement<CharString, bool>>>::_hash       hash_map.h         85   0x4a1dbd9 
4 HashMap<CharString, bool, HashMapHasherDefault, HashMapComparatorDefault<CharString>, DefaultTypedAllocator<HashMapElement<CharString, bool>>>::_lookup_pos hash_map.h         106  0x4a1d8d7 
5 HashMap<CharString, bool, HashMapHasherDefault, HashMapComparatorDefault<CharString>, DefaultTypedAllocator<HashMapElement<CharString, bool>>>::has         hash_map.h         310  0x4a14788 
6 Main::setup                                                                                                                                                 main.cpp           2115 0x4a088d3 
7 main                                                                                                                                                        godot_linuxbsd.cpp 62   0x497f058 
```

The reason is that CharString decided to not create a pointer at all to save memory. Hence when hash_djb2 tries to read the first byte, it crashes.

### Minimal reproduction project

N / A
#ifdef REAL_T_IS_DOUBLE
	return hash_murmur3_one_double(p_in, p_seed);
#else
	return hash_murmur3_one_float(p_in, p_seed);
#endif
}
static _FORCE_INLINE_ uint32_t hash_rotl32(uint32_t x, int8_t r) {
	return (x << r) | (x >> (32 - r));
}
static _FORCE_INLINE_ uint32_t hash_fmix32(uint32_t h) {
	h ^= h >> 16;
	h *= 0x85ebca6b;
	h ^= h >> 13;
	h *= 0xc2b2ae35;
	h ^= h >> 16;
	return h;
}
static _FORCE_INLINE_ uint32_t hash_murmur3_buffer(const void *key, int length, const uint32_t seed = HASH_MURMUR3_SEED) {
	
	const uint8_t *data = (const uint8_t *)key;
	const int nblocks = length / 4;
	uint32_t h1 = seed;
	const uint32_t c1 = 0xcc9e2d51;
	const uint32_t c2 = 0x1b873593;
	const uint32_t *blocks = (const uint32_t *)(data + nblocks * 4);