fix dedicated server crashes

Author: brachy84

src/main/java/com/cleanroommc/modularui/api/MCHelper.java

@@ -5,10 +5,10 @@
 import com.cleanroommc.modularui.api.drawable.IKey;
 
 import net.minecraft.client.Minecraft;
-import net.minecraft.client.entity.EntityPlayerSP;
 import net.minecraft.client.gui.FontRenderer;
 import net.minecraft.client.gui.GuiScreen;
 import net.minecraft.client.util.ITooltipFlag;
+import net.minecraft.entity.player.EntityPlayer;
 import net.minecraft.item.ItemStack;
 import net.minecraft.util.text.TextFormatting;
 import net.minecraftforge.fluids.Fluid;
@@ -33,7 +33,7 @@ public static boolean hasMc() {
         return Minecraft.getMinecraft();
     }
 
-    public static @Nullable EntityPlayerSP getPlayer() {
+    public static @Nullable EntityPlayer getPlayer() {
         if (hasMc()) {
             return getMc().player;
         }
@@ -42,7 +42,7 @@ public static boolean hasMc() {
 
     public static boolean closeScreen() {
         if (!hasMc()) return false;
-        EntityPlayerSP player = getPlayer();
+        EntityPlayer player = getPlayer();
         if (player != null) {
             player.closeScreen();
             return true;

src/main/java/com/cleanroommc/modularui/screen/viewport/ModularGuiContext.java

@@ -17,8 +17,8 @@
 import com.cleanroommc.modularui.screen.UISettings;
 
 import net.minecraft.client.Minecraft;
-import net.minecraft.client.entity.EntityPlayerSP;
 import net.minecraft.client.gui.GuiScreen;
+import net.minecraft.entity.player.EntityPlayer;
 
 import org.jetbrains.annotations.ApiStatus;
 import org.jetbrains.annotations.NotNull;
@@ -255,7 +255,7 @@ public boolean hasDraggable() {
     }
 
     public boolean isMouseItemEmpty() {
-        EntityPlayerSP player = MCHelper.getPlayer();
+        EntityPlayer player = MCHelper.getPlayer();
         return player == null || player.inventory.getItemStack().isEmpty();
     }
 

src/main/java/com/cleanroommc/modularui/value/sync/ModularSyncManager.java

@@ -1,6 +1,7 @@
 package com.cleanroommc.modularui.value.sync;
 
 import com.cleanroommc.modularui.ModularUI;
+import com.cleanroommc.modularui.network.NetworkUtils;
 import com.cleanroommc.modularui.screen.ClientScreenHandler;
 import com.cleanroommc.modularui.screen.ModularContainer;
 import com.cleanroommc.modularui.widgets.slot.SlotGroup;
@@ -62,7 +63,7 @@ public void detectAndSendChanges(boolean init) {
     }
 
     public void onClose() {
-        if (ClientScreenHandler.guiIsClosing) {
+        if (NetworkUtils.isClient() && ClientScreenHandler.guiIsClosing) {
             this.panelSyncManagerMap.values().forEach(PanelSyncManager::onClose);
         }
     }