Fix potential memory leak on Apple platforms (#1130)

In XR.mm when the call to `CVMetalTextureCacheCreateTextureFromImage` fails, the texture reference is not being released. In the Xcode AR example the texture reference is explicitly released when `CVMetalTextureCacheCreateTextureFromImage` fails, so we should probably do the same thing to make sure no memory is being leaked.

Author: docEdub

Dependencies/xr/Source/ARKit/XR.mm

@@ -334,6 +334,7 @@ - (CVMetalTextureRef)getCameraTexture:(CVPixelBufferRef)pixelBuffer plane:(int)p
         // Create a texture from the corresponding plane.
         auto status = CVMetalTextureCacheCreateTextureFromImage(kCFAllocatorDefault, textureCache, pixelBuffer, nil, pixelFormat, planeWidth, planeHeight, planeIndex, &texture);
         if (status != kCVReturnSuccess) {
+            CVBufferRelease(texture);
             return nil;
         }