currfp returns fp_invalid when fp is not known, and does not use it

pattern2.cpp

@@ -355,6 +355,7 @@ int fieldval_uniq(cell *c) {
     return gmod(p.first * torusconfig::dx + p.second * torusconfig::dy, torusconfig::qty);
     }
   else if(binarytiling || archimedean) return 0;
+  else if(&currfp == &fp_invalid) return 0;
   else if(ctof(c) || NONSTDVAR) return c->master->fieldval/S7;
   else {
     int z = 0;