No warning about missing LRUD measurements

[jedwards1211]

Walls allows typing -- to indicate an LRUD measurement is omitted. But it also accepts less than four measurements, like *2 3 4* without warning the user. It even accepts zero measurements **, < >, etc. It also infers an omitted measurements when there are commas with no number between, like *,,,*.

This is bad because whoever entered the data may have omitted a measurement by accident. For example they may have typed *2 3 4* when they meant *2 3 4 5*, or <1,2,,4> when they meant <1,2,3,4>. There is quite a bit of questionable data in the wild because of this. Walls should warn the user and encourage them to explicitly indicate a measurement is omitted by using --.