Null free segfault before renderer is initialized

## Version of Dear PyGui

Version: 1.11.1 (pip wheel), 2.1.0
Operating System: Ubuntu 24.04 (WSL2, Mesa llvmpipe)

## My Issue/Question

Callling `dpg.add_raw_texture` before the viewport/renderer is initialized causes a hard crash when the texture item is destroyed. The raw texture’s destructor always calls `FreeTexture`, which forwards to `glDeleteTextures`. In this code path the OpenGL loader (gl3w) has not been initialized yet, so `dlDeleteTextures` is a null function pointer and the process segfaults. The crash happens even when the raw texture never created a GL texture (e.g. because we delete it immediately).

Relevant sources:
* `mvRawTexture::~mvRawTexture()` in mvTextureItems.cpp (unconditionally calls `FreeTexture(_texture)`)
* `FreeTexture` implementations (mvUtilities_linux.cpp, mvUtilities_win32.cpp, mvUtilities_apple.mm) which unconditionally call the GL driver.

**To Reproduce**
1. Start a fresh Python session with Dear PyGui 1.11.1.
2. Run the minimal script below (note there is no viewport setup yet).
3. Python terminates with SIGSEGV inside `_dearpygui.so` → `FreeTexture` → `glDeleteTextures`.

**Expected behavior**
Destroying a raw texture before the viewport/renderer is available should be a no-op, not a hard crash. Dear PyGui should either defer GL cleanup until the context exists or skip the `glDeleteTextures` call when `_texture` is null/uninitialized.

## Screenshots/Video

**Standalone, minimal, complete and verifiable example**

```python
import numpy as np
import dearpygui.dearpygui as dpg

dpg.create_context()

with dpg.texture_registry():
data = np.zeros((4,), dtype=np.float32)
tex_id = dpg.add_raw_texture(1, 1, data)
dpg.delete_item(tex_id) # <- segfault inside FreeTexture/glDeleteTextures

print("unreachable")
```

But any solution that avoids calling into GL before the loader/context is ready would work. Let me know if you need additional traces or testing on other platforms.