java.lang.NullPointerException at com.android.build.gradle.internal.ndk.NdkHandler.getPlatformVersion

Question

I upgraded my android studio to:

Android Studio Bumblebee | 2021.1.1 Patch 1

and now my project does not build anymore with two error that I can't understand.

First I get this:

cvc-complex-type.2.4.d: Invalid content was found starting with element 'base-extension'. No child element is expected at this point.

What is it? I don't even know which file is causing the issue.

Second, I get a weird null pointer exception looking for the NDK version

Caused by: java.lang.NullPointerException
at com.android.build.gradle.internal.ndk.NdkHandler.getPlatformVersion(NdkHandler.java:121)

I tried this thread which tells me to install the NDK manually and change my local.properties to this but it did not work either.

Gradle sync failed: A problem occurred configuring project ':lib'

sdk.dir=C\:\\Users\\<user>\\AppData\\Local\\Android\\Sdk
ndk.dir=C\:\\Users\\<user>\\AppData\\Local\\Android\\Sdk\\ndk\\23.1.7779620

Any clues?

thank you.