domdisplay: Adjust version comparison

My commit id '9cba9b68' forgot to test whether the condition that the
new version compare statement would be avoiding would be true - that
is that the port in use is 5900 and thus would result in the erroneous
printing of port 0 (zero).

Additionally, it seems the missing :0 was a bug as commit id '31b140eb'
has restored the :0 to the end of the output