Prevent mixins from crashing the game when there are missing mods (#9916)

1.20.1 backport of 49.0.14

src/main/java/net/minecraftforge/client/ForgeHooksClient.java

@@ -512,7 +512,7 @@ public class ForgeHooksClient
     public static void fillNormal(int[] faceData, Direction facing, boolean calculateNormals)
     {
         Vector3f v2;
-        if (calculateNormals || ForgeConfig.CLIENT.calculateAllNormals.get()) {
+        if (calculateNormals || ForgeConfig.CLIENT.calculateAllNormals()) {
             Vector3f v1 = getVertexPos(faceData, 3);
             Vector3f t1 = getVertexPos(faceData, 1);
             v2 = getVertexPos(faceData, 2);

src/main/java/net/minecraftforge/client/loading/ClientModLoader.java

@@ -5,7 +5,6 @@
 
 package net.minecraftforge.client.loading;
 
-
 import java.io.File;
 import java.util.ArrayList;
 import java.util.Collections;
@@ -119,12 +118,8 @@ public class ClientModLoader
     public static boolean completeModLoading()
     {
         var warnings = ModLoader.get().getWarnings();
-        boolean showWarnings = true;
-        try {
-            showWarnings = ForgeConfig.CLIENT.showLoadWarnings.get();
-        } catch (NullPointerException | IllegalStateException e) {
-            // We're in an early error state, config is not available. Assume true.
-        }
+        boolean showWarnings = ForgeConfig.CLIENT.showLoadWarnings();
+
         if (!showWarnings) {
             //User disabled warning screen, as least log them
             if (!warnings.isEmpty()) {

src/main/java/net/minecraftforge/common/ForgeConfig.java

@@ -158,6 +158,16 @@ public class ForgeConfig {
 
             builder.pop();
         }
+
+        // Allow these to be called before the config is loaded because its used before loading the error screens.
+        // Prevents a ton of spam when an error screen is displayed.
+        public final boolean calculateAllNormals() {
+            return clientSpec.isLoaded() ? calculateAllNormals.get() : calculateAllNormals.getDefault();
+        }
+
+        public final boolean showLoadWarnings() {
+            return clientSpec.isLoaded() ? showLoadWarnings.get() : showLoadWarnings.getDefault();
+        }
     }
 
     static final ForgeConfigSpec clientSpec;