diff --git a/HMCLCore/src/main/java/org/jackhuang/hmcl/download/DefaultCacheRepository.java b/HMCLCore/src/main/java/org/jackhuang/hmcl/download/DefaultCacheRepository.java
index 2bbab5257..f11942ed5 100644
--- a/HMCLCore/src/main/java/org/jackhuang/hmcl/download/DefaultCacheRepository.java
+++ b/HMCLCore/src/main/java/org/jackhuang/hmcl/download/DefaultCacheRepository.java
@@ -63,7 +63,7 @@ public class DefaultCacheRepository extends CacheRepository {
         lock.writeLock().lock();
         try {
             if (Files.isRegularFile(indexFile))
-                index = JsonUtils.GSON.fromJson(FileUtils.readText(indexFile.toFile()), Index.class);
+                index = JsonUtils.fromNonNullJson(FileUtils.readText(indexFile.toFile()), Index.class);
             else
                 index = new Index();
         } catch (IOException | JsonParseException e) {
@@ -240,13 +240,13 @@ public class DefaultCacheRepository extends CacheRepository {
         }
     }
 
-    private class LibraryIndex {
+    private class LibraryIndex implements Validation {
         private final String name;
         private final String hash;
         private final String type;
 
         public LibraryIndex() {
-            this(null, null, null);
+            this("", "", "");
         }
 
         public LibraryIndex(String name, String hash, String type) {
@@ -255,18 +255,27 @@ public class DefaultCacheRepository extends CacheRepository {
             this.type = type;
         }
 
+        @NotNull
         public String getName() {
             return name;
         }
 
+        @NotNull
         public String getHash() {
             return hash;
         }
 
+        @NotNull
         public String getType() {
             return type;
         }
 
+        @Override
+        public void validate() throws JsonParseException, TolerableValidationException {
+            if (name == null || hash == null || type == null)
+                throw new JsonParseException("Index.LibraryIndex.* cannot be null");
+        }
+
         @Override
         public boolean equals(Object o) {
             if (this == o) return true;
diff --git a/HMCLCore/src/main/java/org/jackhuang/hmcl/game/Arguments.java b/HMCLCore/src/main/java/org/jackhuang/hmcl/game/Arguments.java
index 0273d0c81..093a1ff26 100644
--- a/HMCLCore/src/main/java/org/jackhuang/hmcl/game/Arguments.java
+++ b/HMCLCore/src/main/java/org/jackhuang/hmcl/game/Arguments.java
@@ -23,11 +23,7 @@ import org.jackhuang.hmcl.util.Lang;
 import org.jackhuang.hmcl.util.platform.OperatingSystem;
 import org.jetbrains.annotations.Nullable;
 
-import java.util.Arrays;
-import java.util.Collections;
-import java.util.LinkedList;
-import java.util.List;
-import java.util.Map;
+import java.util.*;
 import java.util.stream.Collectors;
 
 /**
@@ -99,7 +95,7 @@ public final class Arguments {
     }
 
     public static List<String> parseStringArguments(List<String> arguments, Map<String, String> keys) {
-        return arguments.stream().flatMap(str -> new StringArgument(str).toString(keys, Collections.emptyMap()).stream()).collect(Collectors.toList());
+        return arguments.stream().filter(Objects::nonNull).flatMap(str -> new StringArgument(str).toString(keys, Collections.emptyMap()).stream()).collect(Collectors.toList());
     }
 
     public static List<String> parseArguments(List<Argument> arguments, Map<String, String> keys) {
@@ -107,7 +103,7 @@ public final class Arguments {
     }
 
     public static List<String> parseArguments(List<Argument> arguments, Map<String, String> keys, Map<String, Boolean> features) {
-        return arguments.stream().flatMap(arg -> arg.toString(keys, features).stream()).collect(Collectors.toList());
+        return arguments.stream().filter(Objects::nonNull).flatMap(arg -> arg.toString(keys, features).stream()).collect(Collectors.toList());
     }
 
     public static final List<Argument> DEFAULT_JVM_ARGUMENTS;
diff --git a/HMCLCore/src/main/java/org/jackhuang/hmcl/game/RuledArgument.java b/HMCLCore/src/main/java/org/jackhuang/hmcl/game/RuledArgument.java
index 0abcc1ca3..81f0e6ca2 100644
--- a/HMCLCore/src/main/java/org/jackhuang/hmcl/game/RuledArgument.java
+++ b/HMCLCore/src/main/java/org/jackhuang/hmcl/game/RuledArgument.java
@@ -23,10 +23,7 @@ import com.google.gson.reflect.TypeToken;
 import org.jackhuang.hmcl.util.Immutable;
 
 import java.lang.reflect.Type;
-import java.util.ArrayList;
-import java.util.Collections;
-import java.util.List;
-import java.util.Map;
+import java.util.*;
 import java.util.stream.Collectors;
 
 /**
@@ -69,6 +66,7 @@ public class RuledArgument implements Argument {
     public List<String> toString(Map<String, String> keys, Map<String, Boolean> features) {
         if (CompatibilityRule.appliesToCurrentEnvironment(rules, features) && value != null)
             return value.stream()
+                    .filter(Objects::nonNull)
                     .map(StringArgument::new)
                     .map(str -> str.toString(keys, features).get(0))
                     .collect(Collectors.toList());