DRILL-3268: queries with empty OVER() clause return empty result set

exec/java-exec/src/main/java/org/apache/drill/exec/physical/impl/window/WindowFrameRecordBatch.java

@@ -190,10 +190,14 @@ public IterOutcome innerNext() {
             this.schema = incoming.getSchema();
           }
         case OK:
-          batches.add(new WindowDataBatch(incoming, context));
+          if (incoming.getRecordCount() > 0) {
+            batches.add(new WindowDataBatch(incoming, context));
+          } else {
+            logger.trace("incoming has 0 records, it won't be added to batches");
+          }
           break;
         default:
-          throw new UnsupportedOperationException("Unsupported upstrean state " + upstream);
+          throw new UnsupportedOperationException("Unsupported upstream state " + upstream);
       }
     }
 
@@ -241,6 +245,10 @@ protected void buildSchema() throws SchemaChangeException {
     } catch (IOException | ClassTransformationException e) {
       throw new SchemaChangeException("Exception when creating the schema", e);
     }
+
+    if (incoming.getRecordCount() > 0) {
+      batches.add(new WindowDataBatch(incoming, getContext()));
+    }
   }
 
   private WindowFramer createFramer(VectorAccessible batch) throws SchemaChangeException, IOException, ClassTransformationException {