Neural Monkey does not throw exception when main.initial_variables contains nonexistent path.

[varisd]

When running neuralmonkey-train (and possibly *run) with main.initial_variables set to nonexistent path, Neural Monkey does not throw an exception and continues with execution (probably with randomly initialized variables instead). This does not happen, if the variables directory exists and only the file prefix is incorrect.

e.g.:
bin/neuralmonkey-train tests/bpe.ini -s 'main.initial_variables=["some-directory/variables.data"]'
(If "some-directory" does not exist, this runs normally even though it should fail.)
(If "some-directory" exists and variables.data* is nonexistent, neuralmonkey-train properly trains.)