ConcurrentModificationException | java.util.ArrayList$Itr in next

[foxwoosh]

Glide Version: 4.11.0

Integration libraries: OkHttp3

Device/Android Version: Redmi Note 4 Android 7.0

Issue details / Repro steps / Use case background: don't know how to reproduce this exception, sadly.

Stack trace / LogCat:

java.util.ConcurrentModificationException: null
    at java.util.ArrayList$Itr.next(ArrayList.java:831)
    at com.bumptech.glide.Glide.trimMemory(Glide.java:688)
    at com.bumptech.glide.Glide.onTrimMemory(Glide.java:900)
    at android.app.Application.onTrimMemory(Application.java:138)
    at android.app.ActivityThread.handleTrimMemory(ActivityThread.java:5120)
    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1741)
    at android.os.Handler.dispatchMessage(Handler.java:102)
    at android.os.Looper.loop(Looper.java:165)
    at android.app.ActivityThread.main(ActivityThread.java:6375)
    at java.lang.reflect.Method.invoke(Method.java)
    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:912)
    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:802)

[sjudd]

Duplicate of #4162