Crash on importing Vuforia core samples asset as Vuforia resource file doesn't generate on enabling AR support settings

Steps to Repro:
1. File > build settings > player settings
2. XR settings > enable Vuforia augmented reality supported setting
3. Observe the resource files are not generating
4. Import Vuforia core samples asset > project window > delete all files >
5. Observe resources folder remains after deletion > delete resources folder again
6. Disable Vuforia AR supported setting >import package again > observe the crash

Expected result:
Resource files should be generated and deleted when the setting is toggled

Workaround:
1. Enable Vuforia augmented reality supported setting
2. Restart Unity > Now disabling and re-enabling the settings will generate the resource files

Note:
1. If the setting is disabled on restarting unity resource file is not generated
2. This leads to Vuforia namespace missing errors if sample packages are downloaded from asset store

Occurring with:
2018.1.0b1, 2018.1.0a7

Working with:
2018.1.0a6, 2018.1.0a4, 2018.1.0a1, 2017.3.0f3

Environment:
Occurring on Windows and Mac