Only call event when turning pressure plate on. Fixes BUKKIT-3881

src/main/java/net/minecraft/server/BlockPressurePlateBinary.java

@@ -43,7 +43,8 @@ public class BlockPressurePlateBinary extends BlockPressurePlateAbstract {
             while (iterator.hasNext()) {
                 Entity entity = (Entity) iterator.next();
 
-                // CraftBukkit start - Fire interact event when turning on a pressure plate
+                // CraftBukkit start - Call interact event when turning on a pressure plate
+                if (this.c(world.getData(i, j, k)) == 0) {
                     org.bukkit.World bworld = world.getWorld();
                     org.bukkit.plugin.PluginManager manager = world.getServer().getPluginManager();
                     org.bukkit.event.Cancellable cancellable;
@@ -59,6 +60,7 @@ public class BlockPressurePlateBinary extends BlockPressurePlateAbstract {
                     if (cancellable.isCancelled()) {
                         continue;
                     }
+                }
                 // CraftBukkit end
 
                 if (!entity.at()) {