KivyMD MDTabs - not covering full width of the window

[trueexplorer13]

            ![SharedScreenshot](https://user-images.githubusercontent.com/84591958/119433905-ff261180-bccb-11eb-9edc-2055b667d036.jpg)

[trueexplorer13]

`<Tab>:
    MDLabel:
        id: label
        text: "Welcome to Main Screen"
        halign: 'center'

MDBoxLayout:
    orientation: 'vertical'

    MDToolbar:
        title: 'WhatsApp'
        right_action_items: [['magnify', lambda x: print('Magnify')], ['chat', lambda x: print('Chat')], ['dots-vertical', lambda x: print('Menu')]]

    MDTabs:
        id: android_tabs
        on_tab_switch: app.on_tab_switch(*args)
        Tab:
            text: 'CALLS'
        Tab:
            text: 'CHATS'
        Tab:
            text: 'CONTACTS'

`