New logical plan: uidOnlySchema bug in LOGenerate

The following script fail:

a = load '1.txt' as (a0:int, a1, a2:bag{});
b = foreach a generate a0 as b0, a1 as b1, flatten(a2) as b2:int;
c = filter b by b0==1;
d = foreach c generate b0+1, b2;
dump d;

Error message:
Caused by: org.apache.pig.impl.logicalLayer.FrontendException: ERROR 2239: Structure of schema change. Original: null#1:int,null#2:bytearray,null#5:int Now: b0#1:int,b1#114:NULL
at org.apache.pig.newplan.logical.relational.LogicalSchema.mergeUid(LogicalSchema.java:364)
at org.apache.pig.newplan.logical.relational.LOGenerate.getSchema(LOGenerate.java:170)
at org.apache.pig.newplan.logical.optimizer.SchemaResetter.visit(SchemaResetter.java:89)
at org.apache.pig.newplan.logical.relational.LOGenerate.accept(LOGenerate.java:225)
at org.apache.pig.newplan.DependencyOrderWalker.walk(DependencyOrderWalker.java:75)
at org.apache.pig.newplan.logical.optimizer.SchemaResetter.visit(SchemaResetter.java:76)
at org.apache.pig.newplan.logical.relational.LOForEach.accept(LOForEach.java:71)
at org.apache.pig.newplan.DependencyOrderWalker.walk(DependencyOrderWalker.java:75)
at org.apache.pig.newplan.PlanVisitor.visit(PlanVisitor.java:50)
at org.apache.pig.newplan.logical.optimizer.SchemaPatcher.transformed(SchemaPatcher.java:43)
at org.apache.pig.newplan.optimizer.PlanOptimizer.optimize(PlanOptimizer.java:112)
... 13 more