Fix null dereference on error in iOS CameraDevice (#1649)

The \�rror\ variable passed to \
ewRenderPipelineStateWithDescriptor\ may be nil even when the call
fails. This guards against dereferencing nil when building the error
message string.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: CedricGuillemet

Plugins/NativeCamera/Source/Apple/CameraDevice.mm

@@ -412,7 +412,7 @@ fragment float4 fragmentShader(RasterizerData in [[stage_in]],
 
             if (!m_impl->cameraPipelineState) {
                 return arcana::task_from_error<CameraDimensions>(std::make_exception_ptr(std::runtime_error{
-                    std::string("Failed to create camera pipeline state: ") + [error.localizedDescription cStringUsingEncoding:NSASCIIStringEncoding]}));
+                    std::string("Failed to create camera pipeline state") + (error ? std::string(": ") + [error.localizedDescription cStringUsingEncoding:NSASCIIStringEncoding] : "")}));
             }
 
             m_impl->isInitialized = true;