Fix for empty device list

Author: raub

index.d.ts

@@ -1186,7 +1186,7 @@ declare module "opencl-raub" {
 	 */
 	const getDeviceIDs: (
 		platform: TClPlatform,
-		device_type: number,
+		device_type?: number, // default is `cl.DEVICE_TYPE_ALL`
 	) => TDevice[];
 
 	/**

src/cpp/device.cpp

@@ -17,6 +17,11 @@ JS_METHOD(getDeviceIDs) { NAPI_ENV;
 	cl_uint n = 0;
 	CHECK_ERR(clGetDeviceIDs(platform, type, 0, nullptr, &n));
 
+	Napi::Array deviceArray = Napi::Array::New(env);
+	if (!n) {
+		RET_VALUE(deviceArray);
+	}
+	
 	std::unique_ptr<cl_device_id[]> devices(new cl_device_id[n]);
 	CHECK_ERR(clGetDeviceIDs(
 		platform,
@@ -26,7 +31,6 @@ JS_METHOD(getDeviceIDs) { NAPI_ENV;
 		nullptr
 	));
 
-	Napi::Array deviceArray = Napi::Array::New(env);
 	for (uint32_t i = 0; i < n; i++) {
 		// This is a noop for root-level devices but properly retains sub-devices.
 		CHECK_ERR(clRetainDevice(devices[i]));