java.lang.RuntimeException: Stack empty

[rainoftime]

Hi, for the following formula
ostrich 2b3eb9b

(set-logic QF_LRA)
(check-sat)
(pop 1)

sat
 error
 java.lang.RuntimeException: Stack empty
 	at scala.sys.package$.error(package.scala:27)
 	at scala.collection.mutable.ArrayStack.pop(ArrayStack.scala:118)
 	at ap.SimpleAPI.popHelp(SimpleAPI.scala:4008)
 	at ap.SimpleAPI.pop(SimpleAPI.scala:3993)
 	at ap.parser.SMTParser2InputAbsy.pop(SMTParser2InputAbsy.scala:875)
 	at ap.parser.SMTParser2InputAbsy$$anonfun$ap$parser$SMTParser2InputAbsy$$apply$4.apply$mcVI$sp(SMTParser2InputAbsy.scala:1456)
 	at ap.parser.SMTParser2InputAbsy.ap$parser$SMTParser2InputAbsy$$apply(SMTParser2InputAbsy.scala:1455)
 	at ap.parser.SMTParser2InputAbsy$$anon$1.commandHook(SMTParser2InputAbsy.scala:536)
 	at ap.parser.smtlib.CUP$parser$actions.CUP$parser$do_action(parser.java:1289)
 	at ap.parser.smtlib.parser.do_action(parser.java:419)
 	at java_cup.runtime.lr_parser.parse(lr_parser.java:584)
 	at ap.parser.smtlib.parser.pScriptC(parser.java:441)
 	at ap.parser.SMTParser2InputAbsy.processIncrementally(SMTParser2InputAbsy.scala:548)
 	at ap.CmdlMain$$anonfun$7.apply(CmdlMain.scala:568)
 	at ap.CmdlMain$$anonfun$7.apply(CmdlMain.scala:566)
 	at ap.SimpleAPI$.withProver(SimpleAPI.scala:169)
 	at ap.CmdlMain$.proveMultiSMT(CmdlMain.scala:566)
 	at ap.CmdlMain$.proveProblems(CmdlMain.scala:598)
 	at ap.CmdlMain$$anonfun$doMain$2.apply(CmdlMain.scala:934)
 	at ap.CmdlMain$$anonfun$doMain$2.apply(CmdlMain.scala:932)
 	at scala.collection.mutable.ResizableArray$class.foreach(ResizableArray.scala:59)
 	at scala.collection.mutable.ArrayBuffer.foreach(ArrayBuffer.scala:48)
 	at ap.CmdlMain$.doMain(CmdlMain.scala:932)
 	at ap.CmdlMain$.main(CmdlMain.scala:882)
 	at ostrich.OstrichMain$.main(OstrichMain.scala:37)
 	at ostrich.OstrichMain.main(OstrichMain.scala)