Fix null display when no version history

Should've been null checked since I made it nullable. String concat
saved us any real damage and so all we saw was "null" shown to users.
Quick check and now we don't.

Spigot-Server-Patches/0019-Add-version-history-to-version-command.patch

@@ -1,25 +1,26 @@
-From 5740e3f1fbd1bcad809d4394f437ffffa3b87bed Mon Sep 17 00:00:00 2001
+From 112fed4d2354c631d78ee23707749acf131615df Mon Sep 17 00:00:00 2001
 From: Kyle Wood <demonwav@gmail.com>
 Date: Thu, 1 Mar 2018 19:37:52 -0600
 Subject: [PATCH] Add version history to version command
 
 
 diff --git a/src/main/java/com/destroystokyo/paper/PaperVersionFetcher.java b/src/main/java/com/destroystokyo/paper/PaperVersionFetcher.java
-index ded51d042..e0bd79f60 100644
+index ded51d042..513cddb9b 100644
 --- a/src/main/java/com/destroystokyo/paper/PaperVersionFetcher.java
 +++ b/src/main/java/com/destroystokyo/paper/PaperVersionFetcher.java
-@@ -25,7 +25,9 @@ public class PaperVersionFetcher implements VersionFetcher {
+@@ -25,7 +25,10 @@ public class PaperVersionFetcher implements VersionFetcher {
      @Override
      public String getVersionMessage(@Nonnull String serverVersion) {
          String[] parts = serverVersion.substring("git-Paper-".length()).split("[-\\s]");
 -        return getUpdateStatusMessage("PaperMC/Paper", GITHUB_BRANCH_NAME, parts[0]);
 +        String updateMessage = getUpdateStatusMessage("PaperMC/Paper", GITHUB_BRANCH_NAME, parts[0]);
++        String history = getHistory();
 +
-+        return getHistory() + "\n" + updateMessage;
++        return history != null ? history + "\n" + updateMessage : updateMessage;
      }
  
      private static @Nullable String getMinecraftVersion() {
-@@ -112,4 +114,19 @@ public class PaperVersionFetcher implements VersionFetcher {
+@@ -112,4 +115,19 @@ public class PaperVersionFetcher implements VersionFetcher {
              return -1;
          }
      }