NPE when using stream name to refer to attributes in aggregation join queries

[niveathika]

Description:
$subject, works if a reference is used. Seems the optimisation reference stream name is not updated.

osgi> [2019-09-09 14:02:39,413] ERROR {io.siddhi.distribution.core.internal.StreamProcessorDeployer} - io.siddhi.core.exception.SiddhiAppCreationException: Error on 'SalesOverLast10days' @ Line: 53. Position: 31, near 'PastSalesStream.categoryName'. io.siddhi.distribution.core.internal.exception.SiddhiAppDeploymentException: io.siddhi.core.exception.SiddhiAppCreationException: Error on 'SalesOverLast10days' @ Line: 53. Position: 31, near 'PastSalesStream.categoryName'.
	at io.siddhi.distribution.core.internal.StreamProcessorDeployer.deploySiddhiQLFile(StreamProcessorDeployer.java:92)
	at io.siddhi.distribution.core.internal.StreamProcessorDeployer.deploy(StreamProcessorDeployer.java:167)
	at org.wso2.carbon.deployment.engine.internal.DeploymentEngine.lambda$deployArtifacts$0(DeploymentEngine.java:291)
	at java.util.ArrayList.forEach(ArrayList.java:1257)
	at org.wso2.carbon.deployment.engine.internal.DeploymentEngine.deployArtifacts(DeploymentEngine.java:282)
	at org.wso2.carbon.deployment.engine.internal.RepositoryScanner.sweep(RepositoryScanner.java:112)
	at org.wso2.carbon.deployment.engine.internal.RepositoryScanner.scan(RepositoryScanner.java:68)
	at org.wso2.carbon.deployment.engine.internal.SchedulerTask.run(SchedulerTask.java:43)
	at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511)
	at java.util.concurrent.FutureTask.runAndReset(FutureTask.java:308)
	at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.access$301(ScheduledThreadPoolExecutor.java:180)
	at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(ScheduledThreadPoolExecutor.java:294)
	at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
	at java.lang.Thread.run(Thread.java:748)
Caused by: io.siddhi.core.exception.SiddhiAppCreationException: Error on 'SalesOverLast10days' @ Line: 53. Position: 31, near 'PastSalesStream.categoryName'.
	at io.siddhi.core.util.ExceptionUtil.populateQueryContext(ExceptionUtil.java:43)
	at io.siddhi.core.table.record.ExpressionBuilder.buildVariableExecutors(ExpressionBuilder.java:414)
	at io.siddhi.core.table.record.ExpressionBuilder.buildVariableExecutors(ExpressionBuilder.java:147)
	at io.siddhi.core.table.record.ExpressionBuilder.buildVariableExecutors(ExpressionBuilder.java:124)
	at io.siddhi.core.table.record.ExpressionBuilder.build(ExpressionBuilder.java:112)
	at io.siddhi.extension.store.rdbms.RDBMSEventTable.compileCondition(RDBMSEventTable.java:1136)
	at io.siddhi.core.table.record.AbstractQueryableRecordTable.compileCondition(AbstractQueryableRecordTable.java:511)
	at io.siddhi.core.aggregation.AggregationRuntime.compileExpression(AggregationRuntime.java:504)
	at io.siddhi.core.query.processor.stream.window.AggregateWindowProcessor.compileCondition(AggregateWindowProcessor.java:90)
	at io.siddhi.core.util.parser.JoinInputStreamParser.parseInputStream(JoinInputStreamParser.java:282)
	at io.siddhi.core.util.parser.InputStreamParser.parse(InputStreamParser.java:88)
	at io.siddhi.core.util.parser.QueryParser.parse(QueryParser.java:136)
	at io.siddhi.core.util.parser.SiddhiAppParser.parse(SiddhiAppParser.java:254)
	at io.siddhi.core.SiddhiManager.createSiddhiAppRuntime(SiddhiManager.java:85)
	at io.siddhi.core.SiddhiManager.createSiddhiAppRuntime(SiddhiManager.java:95)
	at io.siddhi.distribution.core.internal.StreamProcessorService.deploySiddhiApp(StreamProcessorService.java:69)
	at io.siddhi.distribution.core.internal.StreamProcessorDeployer.deploySiddhiQLFile(StreamProcessorDeployer.java:80)
	... 14 more
Caused by: java.lang.NullPointerException
	at io.siddhi.core.table.record.ExpressionBuilder.buildVariableExecutors(ExpressionBuilder.java:392)
	... 29 more

Affected Siddhi Version:
5.1.3

OS, DB, other environment details and versions:
JDK 1.8.0