empty error message when ending tag missing

[dahaic]

When trying to open xccdf file referencing malformed oval file, where closing tag </definitions> is missing, error message workbench presents to the user is empty.

Output of oscap oval validate test-rhel7-oval.xml (exit code 1):

test-rhel7-oval.xml:57: parser error : Opening and ending tag mismatch: definitions line 15 and oval_definitions
</oval_definitions>
                   ^
test-rhel7-oval.xml:58: parser error : Premature end of data in tag oval_definitions line 1

^

Output of scap-workbench:

Error while opening file. There was a problem with ScanningSession! Failed to reload session. OpenSCAP error message: 

[mpreisler]

Solved by @ybznek in #47