diff --git a/gerrit-server/src/main/java/com/google/gerrit/server/change/PostReview.java b/gerrit-server/src/main/java/com/google/gerrit/server/change/PostReview.java
index 6a87698d67..38070c0236 100644
--- a/gerrit-server/src/main/java/com/google/gerrit/server/change/PostReview.java
+++ b/gerrit-server/src/main/java/com/google/gerrit/server/change/PostReview.java
@@ -315,12 +315,16 @@ public class PostReview implements RestModifyView<RevisionResource, ReviewInput>
       Iterator<CommentInput> listItr = list.iterator();
       while (listItr.hasNext()) {
         CommentInput c = listItr.next();
+        if (c == null) {
+          listItr.remove();
+          continue;
+        }
         if (c.line < 0) {
           throw new BadRequestException(String.format(
               "negative line number %d not allowed on %s",
               c.line, path));
         }
-        c.message = Strings.emptyToNull(c.message).trim();
+        c.message = Strings.nullToEmpty(c.message).trim();
         if (c.message.isEmpty()) {
           listItr.remove();
         }
diff --git a/gerrit-server/src/main/java/com/google/gerrit/server/project/ListChildProjects.java b/gerrit-server/src/main/java/com/google/gerrit/server/project/ListChildProjects.java
index 1910a5e44e..8d1e95f546 100644
--- a/gerrit-server/src/main/java/com/google/gerrit/server/project/ListChildProjects.java
+++ b/gerrit-server/src/main/java/com/google/gerrit/server/project/ListChildProjects.java
@@ -26,6 +26,7 @@ import com.google.inject.Inject;
 
 import org.kohsuke.args4j.Option;
 
+import java.util.Collections;
 import java.util.List;
 import java.util.Map;
 
@@ -96,7 +97,13 @@ public class ListChildProjects implements RestReadView<ProjectResource> {
         node.addChild(key);
       }
     }
-    return getChildProjectsRecursively(projects.get(parent));
+
+    ProjectNode n = projects.get(parent);
+    if (n != null) {
+      return getChildProjectsRecursively(n);
+    } else {
+      return Collections.emptyList();
+    }
   }
 
   private List<ProjectInfo> getChildProjectsRecursively(ProjectNode p) {