XQuery, Handle recursive calls

[ChristianGruen]

With the XQuery and Async Module, the same function can be recursively called. This currently leads to undesired results:

Query:

import module namespace _ = "_" at "_.xqm";
_:_()

_.xqm (xquery:eval)

module namespace _ = "_";
declare function _:_() {
  xquery:eval('import module namespace _ = "_" at "_.xqm"; _:_()')
};

Result:

Improper use? Potential bug? Your feedback is welcome:
Contact: basex-talk@mailman.uni-konstanz.de
Version: BaseX 8.5 beta
Java: Oracle Corporation, 1.8.0_65
OS: Windows 10, amd64
Stack Trace: 
java.lang.NoClassDefFoundError: Could not initialize class org.basex.query.QueryException
    at org.basex.query.QueryError.get(QueryError.java:1342)
    at org.basex.query.QueryContext.iter(QueryContext.java:372)
    at org.basex.query.func.xquery.XQueryEval.eval(XQueryEval.java:136)
    at org.basex.query.func.xquery.XQueryEval.eval(XQueryEval.java:62)
    at org.basex.query.func.xquery.XQueryEval.iter(XQueryEval.java:47)
    at org.basex.query.MainModule.iter(MainModule.java:119)

_.xqm (async:eval)

module namespace _ = "_";
declare function _:_() {
  async:eval('import module namespace _ = "_" at "_.xqm"; _:_()')
};

Result: Creation of new queries; process cannot be stopped without killing BaseX.