Change version 1.7.1 to 18.2:ConcurrentModificationException

[Cleverson Pohlod]

Does anyone know why when migrating from version 1.7.1 to version 1.8.2
error now occurs in the loop of images from pdf?
code:
     Iterator<Entry<String, Object>> it = images.entrySet().iterator();
     while (it.hasNext()) {
        Entry<String, Object> entry = it.next();

error:

java.util.ConcurrentModificationException
at java.util.HashMap$HashIterator.nextEntry(HashMap.java:806)
at java.util.HashMap$EntryIterator.next(HashMap.java:847)
at java.util.HashMap$EntryIterator.next(HashMap.java:845)