Added error-handling to CSVHandler. CSVHandler throws an
UnsupportedOperationException with a fitting message that can be caught.
Replaced string comparison with == by string comparison with equals
Added parent header to csv.
Added error handling for the case that a student dataset does not
contain any parent information.
Inserted parent-testdata into csv.
Changed header name "Erz1StraßeNr" to "Erz1StrasseNr"
Added check for NumberFormatException to check if the postalcode is a
number. Changed postalcode in csv from "Test" to "1".
Changed propertyname from "Erz1StraßeNr" to "Erz1StrasseNr"
Added closeExistingWindow() to prevent an IllegalArgumentException
Merge remote-tracking branch 'upstream/develop' into issue#299
Merge pull request #306 from Junkern/issue#299

Issue#299
If no data is selected that could be printed the method
createByteArrayOutputStream of PDFHandler returns null now.
Added null checks to LendingView and ReturnView.
Replaced generic and deprecated code in PrintingComponent.
Merge pull request #302 from B3nRa/issue#184

Added error-handling to CSVHandler. CSVHandler throws an
Merge pull request #308 from B3nRa/issue#304

If no data is selected that could be printed the method
Merge remote-tracking branch 'upstream/develop' into #291