ST_CreateTopoGeo: non-existent node

[strk]

An input derived from sample dataset in #1274 produces a "non-existent node" exception when feed to ST_CreateTopoGeo.

Robustness issues moving from GEOS to PostGIS, whoa ! :)

Here's the reduced version of the offending input, at the max reduction I was able to perform so far.

MULTILINESTRING(
(
 832709.937 816560.25,
 832705.813 816470.25,
 832661.937 816561.875
),
(
 832705.812 816470.25,
 832709.937 816560.25
),
(
 832661.938 816561.875,
 832705.813 816470.25
))

[strk]

Analisys: second and third segments share a point, and they form a V shape (togheter) First line is a two-segment doing the whole V shape. But while the upper vertices of the V match the ones of second and third lines, the lower corner is slightly offsetted in the X (832705.813 vs 832705.812)

[strk]

Wrong analisys. Actual shape (with topology manually magnified):

[strk]

Fixed by r8148