Error while adding platform. Until i have added app-preference plugin, app was working fine

cordova platform add android --save
Using cordova-fetch for cordova-android@7.0.0
Adding android project…
Creating Cordova project for the Android platform:
Path: platforms\android
Package: com.subex.collegeconnect
Name: College_Connect
Activity: MainActivity
Android target: android-26
Subproject Path: CordovaLib
Subproject Path: app
Android project created with cordova-android@7.0.0
Android Studio project detected
Android Studio project detected
(node:25344) UnhandledPromiseRejectionWarning: SyntaxError: Unexpected token } in JSON at position 1525
at JSON.parse ()
at getJson (C:\Users\Jagadeeshwaran.n\AppData\Roaming\npm\node_modules\cordova\node_modules\cordova-lib\src\plugman\util\metadata.js:29:31)
at Object.exports.get_fetch_metadata (C:\Users\Jagadeeshwaran.n\AppData\Roaming\npm\node_modules\cordova\node_modules\cordova-lib\src\plugman\util\metadata.js:41:24)
at C:\Users\Jagadeeshwaran.n\AppData\Roaming\npm\node_modules\cordova\node_modules\cordova-lib\src\cordova\platform\addHelper.js:343:48
at _fulfilled (C:\Users\Jagadeeshwaran.n\AppData\Roaming\npm\node_modules\cordova\node_modules\cordova-lib\node_modules\q\q.js:787:54)
at self.promiseDispatch.done (C:\Users\Jagadeeshwaran.n\AppData\Roaming\npm\node_modules\cordova\node_modules\cordova-lib\node_modules\q\q.js:816:30)
at Promise.promise.promiseDispatch (C:\Users\Jagadeeshwaran.n\AppData\Roaming\npm\node_modules\cordova\node_modules\cordova-lib\node_modules\q\q.js:749:13)
at C:\Users\Jagadeeshwaran.n\AppData\Roaming\npm\node_modules\cordova\node_modules\cordova-lib\node_modules\q\q.js:810:14
at flush (C:\Users\Jagadeeshwaran.n\AppData\Roaming\npm\node_modules\cordova\node_modules\cordova-lib\node_modules\q\q.js:108:17)
at _combinedTickCallback (internal/process/next_tick.js:131:7)
(node:25344) UnhandledPromiseRejectionWarning: Unhandled promise rejection. This error originated either by throwing inside of an async function without a catch block, or by rejecting a promise which was not handled with .catch(). (rejection id: 1)
(node:25344) [DEP0018] DeprecationWarning: Unhandled promise rejections are deprecated. In the future, promise rejections that are not handled will terminate the Node.js process with a non-zero exit code.