nativeTexture() crashes with SIGSEGV on freed MetalTextureRenderer* — missing nullptr guard

Description
The exported nativeTexture() function in pls_binding.mm is the only renderer API that does not guard against a nullptr renderer argument. When called with a freed or null pointer, it crashes with EXC_BAD_ACCESS (SIGSEGV) / KERN_INVALID_ADDRESS.

Every other exported function in the same file includes a null check:

// ✅ Has null check
EXPORT bool clear(MetalTextureRenderer* renderer, bool clear, uint32_t color) {
    if (renderer == nullptr) { return false; }
    renderer->begin(clear, color);
    return true;
}

// ✅ Has null check
EXPORT rive::Renderer* makeRenderer(MetalTextureRenderer* renderer) {
    if (renderer == nullptr) { return nullptr; }
    return renderer->renderer();
}

// ❌ Missing null check — crashes
EXPORT void* nativeTexture(MetalTextureRenderer* renderer) {
    return (__bridge void*)renderer->currentTargetTexture();
}

Crash Report

Process:               XXXX - [71482]
Code Type:             ARM-64 (Native)
OS Version:            macOS 15.7.3 (24G419)

Crashed Thread:        65  Dispatch queue: com.airplaystudio.mixer.render

Exception Type:        EXC_BAD_ACCESS (SIGSEGV)
Exception Codes:       KERN_INVALID_ADDRESS at 0x00006001e1d78e90

Thread 65 Crashed:
0   rive_native     nativeTexture + 8
1   our_plugin      [RiveTextureBridge registerRendererPointer:asSlot:]_block_invoke + 172

Reproduction Context
This crash occurs when nativeTexture() is called from a render loop on a background dispatch queue while destroyRiveRenderer() runs on the platform thread. The 1-second batched _disposeTexture() Timer in _NativeRenderTexture creates a window where the old MetalTextureRenderer* is freed but external callers may still hold the pointer.

Race window:

1. performLayout() triggers makeRenderTexture() with new dimensions
2. Old renderer is queued for destruction via 1-second Timer
3. External render loop calls nativeTexture(oldRenderer) before onTextureChanged callback fires
4. destroyRiveRenderer() frees the old renderer on the platform thread
5. nativeTexture() dereferences the freed pointer → SIGSEGV

Suggested Fix

 EXPORT void* nativeTexture(MetalTextureRenderer* renderer) {
+    if (renderer == nullptr) { return nullptr; }
     return (__bridge void*)renderer->currentTargetTexture();
 }

Environment
Package: rive_native 0.1.2
Platform: macOS 15.7.3 (ARM64)
Flutter: 3.x
File:
native/src/pls_binding.mm , line 246–249

Start in native/src/pls_binding.mm around lines 246–249 and compare nativeTexture() with the other exported functions’ null checks. Trace the destroyRiveRenderer() and _disposeTexture() lifecycle described in the issue, then reproduce the render-loop and disposal timing if possible. Done means the reported nativeTexture() crash is prevented for the described invalid-renderer calls.