Catch any Throwable, as getErrorMessage can handle anyway

Arvid, previously only Exception's were catched, but the bioclipse.core's StringMatrix is throwing Errors (independent whether that is proper code...), but the method that handles the exception can just as well handle any Throwable, so I changed the catch part.

This should fix an issue my PhD student (Bart) was having where doing

stringMatrix.getColumn("Doesn't exist")

caused the full GroovyConsole to crash.