Do not create nether portals that delete undestroyable blocks

Fixes https://github.com/PaperMC/Paper/issues/5773

patches/server/0439-Protect-Bedrock-and-End-Portal-Frames-from-being-des.patch

@@ -170,3 +170,21 @@ index a087eec747bb355afd627c6042d20440c3e43e1b..bea9c7ac0fe08c3ca3309e8311f192cc
          }
  
          public boolean isSolidRender(BlockGetter world, BlockPos pos) {
+diff --git a/src/main/java/net/minecraft/world/level/portal/PortalForcer.java b/src/main/java/net/minecraft/world/level/portal/PortalForcer.java
+index d5ba2e679ed1858ea18e18feffce50544ae036c2..ca3e143e641933fa6b9499bbaaa1836877d90c52 100644
+--- a/src/main/java/net/minecraft/world/level/portal/PortalForcer.java
++++ b/src/main/java/net/minecraft/world/level/portal/PortalForcer.java
+@@ -209,6 +209,13 @@ public class PortalForcer {
+         for (int j = -1; j < 3; ++j) {
+             for (int k = -1; k < 4; ++k) {
+                 temp.setWithOffset((Vec3i) pos, portalDirection.getStepX() * j + enumdirection1.getStepX() * distanceOrthogonalToPortal, k, portalDirection.getStepZ() * j + enumdirection1.getStepZ() * distanceOrthogonalToPortal);
++                // Paper start - prevent destroying unbreakable blocks
++                if (!com.destroystokyo.paper.PaperConfig.allowBlockPermanentBreakingExploits) {
++                    if (!this.level.getBlockState(temp).isDestroyable()) {
++                        return false;
++                    }
++                }
++                // Paper end - prevent destroying unbreakable blocks
+                 if (k < 0 && !this.level.getBlockState(temp).getMaterial().isSolid()) {
+                     return false;
+                 }