Bad line transformations

[algobardo]

Receiving some exceptions like this:

Something went wrong during transformation of line: {"entryKind":"write-variable","name":{"valueKind":"concrete-string","value":"i"},"value":{"valueKind":"abstract-primitive","value":"1"},"sourceLocation":{"fileName":""},"index":-1}: java.lang.NullPointerException

Problem is when reproducing log files on tajs.Stats$Libs in the symbols_wip branch.
This could be a problem in other branches or a problem introduced by:

• the special jalangi2 version used in that branch
• the special ValueLogger used in that branch
• by the benchmarks (that use symbols!) that we use in that branch

The issue is workarounded at the moment by emitting a warning rather than throwing an exception, the effect of this being discarding a few lines from the log file.