When building with gcc static analyzer enabled, we get the following warning.
Seems the warning is correct (but maybe too cautious).
We even have a check for NULL right in front of line 1121 :
https://github.com/openjdk/jdk/blob/02d7281b93296e7700e215804cb9e2f8341cab06/src/java.instrument/share/native/libinstrument/JPLISAgent.c#L1120
But the jplis_assert just prints a warning message.

The function retransformableEnvironment might return NULL in some special cases
https://github.com/openjdk/jdk/blob/02d7281b93296e7700e215804cb9e2f8341cab06/src/java.instrument/share/native/libinstrument/JPLISAgent.c#L1035
and it seems this is not perfectly handled.

GCC static analyzer warning output :

/jdk/src/java.instrument/share/native/libinstrument/JPLISAgent.c:1121:19: warning: dereference of NULL 'retransformerEnv' [CWE-476] [-Wanalyzer-null-dereference]
 1121 | jvmtierror = (*retransformerEnv)->SetEventNotificationMode(
      | ~^~~~~~~~~~~~~~~~~~
  'setHasRetransformableTransformers': events 1-2
    |
    | 1116 | setHasRetransformableTransformers(JNIEnv * jnienv, JPLISAgent * agent, jboolean has) {
    | | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    | | |
    | | (1) entry to 'setHasRetransformableTransformers'
    | 1117 | jvmtiEnv * retransformerEnv = retransformableEnvironment(agent);
    | | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    | | |
    | | (2) calling 'retransformableEnvironment' from 'setHasRetransformableTransformers'
    |
    +--> 'retransformableEnvironment': events 3-6
           |
           | 1021 | retransformableEnvironment(JPLISAgent * agent) {
           | | ^~~~~~~~~~~~~~~~~~~~~~~~~~
           | | |
           | | (3) entry to 'retransformableEnvironment'
           | 1022 | jvmtiEnv * retransformerEnv = NULL;
           | | ~~~~~~~~~~~~~~~~
           | | |
           | | (4) 'retransformerEnv' is NULL
           |......
           | 1028 | if (agent->mRetransformEnvironment.mJVMTIEnv != NULL) {
           | | ~
           | | |
           | | (5) following 'false' branch...
           |......
           | 1031 | jnierror = (*agent->mJVM)->GetEnv( agent->mJVM,
           | | ~~~~~~~~
           | | |
           | | (6) ...to here
           |
    <------+
    |
  'setHasRetransformableTransformers': events 7-8
    |
    | 1117 | jvmtiEnv * retransformerEnv = retransformableEnvironment(agent);
    | | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    | | |
    | | (7) return of NULL to 'setHasRetransformableTransformers' from 'retransformableEnvironment'
    |......
    | 1121 | jvmtierror = (*retransformerEnv)->SetEventNotificationMode(
    | | ~~~~~~~~~~~~~~~~~~~
    | | |
    | | (8) dereference of NULL 'retransformerEnv'
    |