Fix view distance API handling on negative values

Prior to this change, if a player was ever set to have a negative view
distance, an attempt to set them back to the default would fail, leading
to them appearing to be stuck in that state.

Now we just interpret that negative value as a "reset" to default.

Spigot-Server-Patches/0036-Add-player-view-distance-API.patch

@@ -1,4 +1,4 @@
-From e94c7b36b54d7763f5c7a48d7938925fac5e8ac7 Mon Sep 17 00:00:00 2001
+From fad221dfcc2fc3b1537d43146fab2e3a31ab06d3 Mon Sep 17 00:00:00 2001
 From: Byteflux <byte@byteflux.net>
 Date: Wed, 2 Mar 2016 14:35:27 -0600
 Subject: [PATCH] Add player view distance API
@@ -25,7 +25,7 @@ index 9829cdd89..5b0675718 100644
      // CraftBukkit start
      public String displayName;
 diff --git a/src/main/java/net/minecraft/server/PlayerChunkMap.java b/src/main/java/net/minecraft/server/PlayerChunkMap.java
-index e4ed2e991..cfac05750 100644
+index e4ed2e991..9627a9be0 100644
 --- a/src/main/java/net/minecraft/server/PlayerChunkMap.java
 +++ b/src/main/java/net/minecraft/server/PlayerChunkMap.java
 @@ -47,7 +47,7 @@ public class PlayerChunkMap {
@@ -172,23 +172,32 @@ index e4ed2e991..cfac05750 100644
  
      private void e() {
          this.l = true;
-@@ -503,4 +532,20 @@ public class PlayerChunkMap {
+@@ -503,4 +532,29 @@ public class PlayerChunkMap {
          }
      }
      // CraftBukkit end
 +
 +    // Paper start - Player view distance API
-+    public void updateViewDistance(EntityPlayer player, int toSet) {
++    public void updateViewDistance(EntityPlayer player, int distanceIn) {
 +        final int oldViewDistance = player.getViewDistance();
 +
-+        int viewDistance = MathHelper.clamp(toSet, 3, 32);
-+        if (toSet < 0) {
-+            viewDistance = -1;
++        // This represents the view distance that we will set on the player
++        // It can exist as a negative value
++        int playerViewDistance = MathHelper.clamp(distanceIn, 3, 32);
++
++        // This value is the one we actually use to update the chunk map
++        // We don't ever want this to be a negative
++        int toSet = playerViewDistance;
++
++        if (distanceIn < 0) {
++            playerViewDistance = -1;
++            toSet = world.getPlayerChunkMap().getViewDistance();
 +        }
-+        if (viewDistance != oldViewDistance) {
++
++        if (toSet != oldViewDistance) {
 +            // Order matters
-+            this.setViewDistance(player, viewDistance);
-+            player.setViewDistance(viewDistance);
++            this.setViewDistance(player, toSet);
++            player.setViewDistance(playerViewDistance);
 +        }
 +    }
 +    // Paper end
@@ -215,5 +224,5 @@ index b178fe9aa..a3e2e7fb7 100644
      private final Player.Spigot spigot = new Player.Spigot()
      {
 -- 
-2.15.0
+2.15.0.windows.1