go: make sure the source/sink have the same type as the edges relation

Author: erik-krogh

go/ql/src/experimental/CWE-400/DatabaseCallInLoop.ql

@@ -66,4 +66,5 @@ query predicate edges(CallGraphNode pred, CallGraphNode succ) {
 
 from LoopStmt loop, DatabaseAccess dbAccess
 where edges*(loop, dbAccess.asExpr())
-select dbAccess, loop, dbAccess, "This calls " + dbAccess.toString() + " in a $@.", loop, "loop"
+select dbAccess, loop, dbAccess.asExpr(), "This calls " + dbAccess.toString() + " in a $@.", loop,
+  "loop"