Prevent multiple single-point line solutions

Suggested by @rivimey, we test the case where both lines return singular
point lines and prevent them leaking into our drag solution

Fixes https://gitlab.com/kicad/code/kicad/issues/9555

(cherry picked from commit 38a4894d92)

pcbnew/router/pns_dragger.cpp

@@ -504,12 +504,19 @@ bool DRAGGER::tryWalkaround( NODE* aNode, LINE& aOrig, LINE& aWalk )
 
     WALKAROUND::RESULT wr = walkaround.Route( aWalk );
 
-
     if( wr.statusCcw == WALKAROUND::DONE && wr.statusCw == WALKAROUND::DONE )
     {
-        aWalk = ( wr.lineCw.CLine().Length() < wr.lineCcw.CLine().Length() ? wr.lineCw :
-                                                                             wr.lineCcw );
-        ok    = true;
+        if( wr.lineCw.CLine().PointCount() > 1
+                && wr.lineCw.CLine().Length() < wr.lineCcw.CLine().Length() )
+        {
+            aWalk = wr.lineCw;
+            ok    = true;
+        }
+        else if( wr.lineCcw.CLine().PointCount() > 1 )
+        {
+            aWalk = wr.lineCcw;
+            ok    = true;
+        }
     }
     else if( wr.statusCw == WALKAROUND::DONE && wr.lineCw.CLine().PointCount() > 1 )
     {
@@ -521,6 +528,7 @@ bool DRAGGER::tryWalkaround( NODE* aNode, LINE& aOrig, LINE& aWalk )
         aWalk = wr.lineCcw;
         ok    = true;
     }
+
     return ok;
 }