Fix segmentation fault when calling ZstdOutputStream#setDict(ZstdDictCompress) with null

Author: garydgregory

src/main/native/jni_zstd.c

@@ -286,6 +286,7 @@ JNIEXPORT jint JNICALL Java_com_github_luben_zstd_Zstd_loadDictCompress
  */
 JNIEXPORT jint JNICALL Java_com_github_luben_zstd_Zstd_loadFastDictCompress
   (JNIEnv *env, jclass obj, jlong stream, jobject dict) {
+    if (dict == NULL) return -ZSTD_error_dictionary_wrong;
     jclass dict_clazz = (*env)->GetObjectClass(env, dict);
     jfieldID compress_dict = (*env)->GetFieldID(env, dict_clazz, "nativePtr", "J");
     ZSTD_CDict* cdict = (ZSTD_CDict*)(intptr_t)(*env)->GetLongField(env, dict, compress_dict);

src/test/scala/Zstd.scala

@@ -918,6 +918,14 @@ class ZstdSpec extends AnyFlatSpec with ScalaCheckPropertyChecks {
     }
   }
 
+  "ZstdOutputStream" should s"do not cause a segmentation fault" in {
+    val os  = new ByteArrayOutputStream(100)
+    val zos = new ZstdOutputStream(os)
+    assertThrows[ZstdIOException] {
+      zos.setDict(null.asInstanceOf[ZstdDictCompress])
+    }
+  }
+
   "ZstdDirectBufferCompressingStream" should s"do nothing on double close but throw on writing on closed stream" in {
     val os  = ByteBuffer.allocateDirect(100)
     val zos = new ZstdDirectBufferCompressingStream(os, 1)