add 4 checks for NewWeakGlobalRef() returning NULL

Author: stephengold

src/main/native/glue/com_jme3_bullet_MultiBody.cpp

@@ -140,6 +140,7 @@ JNIEXPORT jlong JNICALL Java_com_jme3_bullet_MultiBody_create
     jmeUserPointer const pUser = new jmeUserInfo(); //dance005
     pUser->m_javaRef = pEnv->NewWeakGlobalRef(object); //dance039
     EXCEPTION_CHK(pEnv, 0);
+    NULL_CHK(pEnv, pUser->m_javaRef, "unable to make reference global", 0)
     pUser->m_group = 0x1;
     pUser->m_groups = 0x1;
     pUser->m_jmeSpace = NULL;

src/main/native/glue/com_jme3_bullet_collision_PhysicsCollisionObject.cpp

@@ -747,6 +747,7 @@ JNIEXPORT void JNICALL Java_com_jme3_bullet_collision_PhysicsCollisionObject_ini
     pUser->m_jmeSpace = NULL;
     pUser->m_javaRef = pEnv->NewWeakGlobalRef(object); //dance041
     // no check for exceptions!
+    NULL_CHK(pEnv, pUser->m_javaRef, "unable to make reference global",)
 }
 
 /*

src/main/native/glue/com_jme3_bullet_collision_shapes_CustomConvexShape.cpp

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2024 jMonkeyEngine
+ * Copyright (c) 2024-2026 jMonkeyEngine
  * All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
@@ -175,6 +175,7 @@ JNIEXPORT jlong JNICALL Java_com_jme3_bullet_collision_shapes_CustomConvexShape_
 
     jweak javaShapeRef = pEnv->NewWeakGlobalRef(javaShape); // TODO leak
     EXCEPTION_CHK(pEnv, 0);
+    NULL_CHK(pEnv, javaShapeRef, "unable to make reference global", 0)
 
     jmeConvexShape *pShape;
     if (heVector == NULL) {

src/main/native/glue/jmeCollisionSpace.cpp

@@ -107,6 +107,7 @@ jmeCollisionSpace::jmeCollisionSpace(JNIEnv *pEnv, jobject javaSpace) {
 
     m_javaSpace = pEnv->NewWeakGlobalRef(javaSpace); // TODO leak
     EXCEPTION_CHK(pEnv,);
+    NULL_CHK(pEnv, m_javaSpace, "unable to make reference global",)
 }
 
 void jmeCollisionSpace::attachThread() {