ST_ClipByBox2D a little less brittle

[pramsey]

Sometimes the function fails like

{
errors: [
"Postgis Plugin: ERROR: Error performing rectangular clipping: 
IllegalArgumentException: Invalid number of points in LinearRing found 3 - must be 0 or >= 4 in 
executeQuery Full sql was: 
'SELECT ST_AsTWKB(ST_Simplify(ST_ClipByBox2D(ST_SnapToGrid("the_geom_webmercator", 0.477731),ST_MakeEnvelope(-539339.6715802038,5057073.791347261,-527109.7470545759,5069303.715872888,3857)), 0.955463),-1) AS geom,"agregado" FROM (select * from table_47_valladolid_recfe) as cdbq WHERE "the_geom_webmercator" && ST_MakeEnvelope(-539339.6715802038,5057073.791347261,-527109.7470545759,5069303.715872888,3857)' "
]

And the problem is not actually feeding the function a geometry with bad rings, it's the GEOS function itself creating them, which isn't great, but since we're bunging up the data anyways, rather than dying we should just keep on cruising.

[pramsey]

Done at r13669