chunk(...) must accept at least one fragment

develop/unbench.lua

@@ -619,7 +619,7 @@ basics.describe_bench(string.format('create and destroy %d entities / spawn_at',
         local fragments = {}
         local components = {}
 
-        local chunk = evo.chunk()
+        local chunk = nil
 
         for i = 1, N do
             entities[i] = spawn_at(chunk, fragments, components)

develop/untests.lua

@@ -647,11 +647,6 @@ do
     assert(evo.insert(e2b, f1, 44))
     assert(evo.insert(e2b, f2, 45))
 
-    do
-        local chunk, entities = evo.chunk()
-        assert(not chunk and not entities)
-    end
-
     do
         local chunk, entities = evo.chunk(f1)
         assert(entities and entities[1] == e1)