Correctly check for null values in EditSession.replaceBlocks()

src/main/java/com/sk89q/worldedit/EditSession.java

@@ -1248,6 +1248,7 @@ public class EditSession {
         Set<BaseBlock> definiteBlockTypes = new HashSet<BaseBlock>();
         Set<Integer> fuzzyBlockTypes = new HashSet<Integer>();
 
+        if (fromBlockTypes != null) {
             for (BaseBlock block : fromBlockTypes) {
                 if (block.getData() == -1) {
                     fuzzyBlockTypes.add(block.getType());
@@ -1255,6 +1256,7 @@ public class EditSession {
                     definiteBlockTypes.add(block);
                 }
             }
+        }
 
         int affected = 0;
 
@@ -1275,10 +1277,18 @@ public class EditSession {
                     for (int z = minZ; z <= maxZ; ++z) {
                         Vector pt = new Vector(x, y, z);
                         BaseBlock curBlockType = getBlock(pt);
+
+                        if (fromBlockTypes == null) {
+                            //replace <to-block>
+                            if (curBlockType.isAir()) {
+                                continue;
+                            }
+                        } else {
                             //replace <from-block> <to-block>
                             if (!definiteBlockTypes.contains(curBlockType) && !fuzzyBlockTypes.contains(curBlockType.getType())) {
                                 continue;
                             }
+                        }
 
                         if (setBlock(pt, toBlock)) {
                             ++affected;
@@ -1290,10 +1300,17 @@ public class EditSession {
             for (Vector pt : region) {
                 BaseBlock curBlockType = getBlock(pt);
 
+                if (fromBlockTypes == null) {
+                    //replace <to-block>
+                    if (curBlockType.isAir()) {
+                        continue;
+                    }
+                } else {
                     //replace <from-block> <to-block>
                     if (!definiteBlockTypes.contains(curBlockType) && !fuzzyBlockTypes.contains(curBlockType.getType())) {
                         continue;
                     }
+                }
 
                 if (setBlock(pt, toBlock)) {
                     ++affected;