Various crashes fixed

core/src/io/anuke/mindustry/maps/generation/FortressGenerator.java

@@ -128,7 +128,7 @@ public class FortressGenerator{
         int maxIndex = (int)(1 + ((float)gen.sector.difficulty / maxDifficulty * (structures.length-2)));
 
         for(int i = maxIndex/2; i < maxIndex; i++){
-            selected.add(structures[i]);
+            selected.add(structures[Math.min(i, structures.length-1)]);
         }
 
         float baseChance = 0.8f / selected.size;

core/src/io/anuke/mindustry/maps/generation/WorldGenerator.java

@@ -242,7 +242,7 @@ public class WorldGenerator{
         int x = sectorX * sectorSize + localX + Short.MAX_VALUE;
         int y = sectorY * sectorSize + localY + Short.MAX_VALUE;
 
-        Block floor;
+        Block floor = Blocks.stone;
         Block wall = Blocks.air;
 
         double ridge = rid.getValue(x, y, 1f / 400f);
@@ -283,7 +283,7 @@ public class WorldGenerator{
             if(iceridge > 0.25 && minDst > lerpDst/1.5f){
                 elevation ++;
             }
-        }else{
+        }else if(minDst > lerpDst/1.5f){
             floor = Blocks.lava;
         }