Ionic3 build Error - upgrading from ionic2 to ioni3

Yes i did make the required changes but still the error persists.

This is my ionic info for now :

global packages:

    @ionic/cli-plugin-proxy : 1.3.1
    @ionic/cli-utils        : 1.4.0
    Cordova CLI             : 6.5.0
    Ionic CLI               : 3.4.0

local packages:

    @ionic/app-scripts              : 1.3.7
    @ionic/cli-plugin-cordova       : 1.4.0
    @ionic/cli-plugin-ionic-angular : 1.3.1
    Cordova Platforms               : android 6.1.2 browser 4.1.0
    Ionic Framework                 : ionic-angular 3.4.0

System:

    Node       : v6.11.0
    OS         : Windows 10
    Xcode      : not installed
    ios-deploy : not installed
    ios-sim    : not installed
    npm        : 5.0.3

and this is the error again :

[WARN] Error occurred during command execution from a CLI plugin (@ionic/cli-plugin-cordova). Your plugins may be out of
date.
[DEBUG] !!! ERROR ENCOUNTERED !!!
Error: Cannot set property 'fixed' of undefined in undefined at line undefined, col undefined, pos undefined
[DEBUG] Error: Cannot set property 'fixed' of undefined in undefined at line undefined, col undefined, pos undefined
at BuildError.Error (native)
at new BuildError
(D:\app\node_modules\@ionic\app-scripts\dist\util\errors.js:16:28)
at taskReject
(D:\app\node_modules\@ionic\app-scripts\dist\worker-process.js:36:22)
at
D:\app\node_modules\@ionic\app-scripts\dist\worker-process.js:14:13
at process._tickCallback (internal/process/next_tick.js:109:7)