Fix #298 - Cope with irregularly shaped imports (e.g. entire worlds)

src/mcedit2/imports.py

@@ -80,6 +80,9 @@ class PendingImportNode(Node, QtCore.QObject):
             object's position, rotation, and scale.
         textureAtlas: TextureAtlas
             The textures and block models used to render the preview of the object.
+        hasHandle: bool
+            True if this import node should have a user-interactive BoxHandle associated
+            with it. This is False for the extra copies displayed by a repeated clone.
 
         Attributes
         ----------

src/mcedit2/util/worldloader.py

@@ -77,5 +77,6 @@ class WorldLoader(object):
         else:
             chunkPositions = self.scene.dimension.chunkPositions()
         for cPos in chunkPositions:
-            for _ in self.scene.workOnChunk(self.scene.dimension.getChunk(*cPos)):
-                yield _
+            if self.scene.dimension.containsChunk(*cPos):
+                for _ in self.scene.workOnChunk(self.scene.dimension.getChunk(*cPos)):
+                    yield _