Use point collision test for zero-length segments

SEG::SquaredDistance( SEG& ) does not do the right thing
for segments with zero length at the moment.

Fixes https://gitlab.com/kicad/code/kicad/-/issues/9791

libs/kimath/include/geometry/shape_segment.h

@@ -78,6 +78,9 @@ public:
     bool Collide( const SEG& aSeg, int aClearance = 0, int* aActual = nullptr,
                   VECTOR2I* aLocation = nullptr ) const override
     {
+        if( aSeg.A == aSeg.B )
+            return Collide( aSeg.A, aClearance, aActual, aLocation );
+
         int min_dist = ( m_width + 1 ) / 2 + aClearance;
         ecoord dist_sq = m_seg.SquaredDistance( aSeg );