fixed errors about underlying_map uninitialized

fake.cpp

@@ -75,6 +75,7 @@ EX namespace fake {
       }
   
     hrmap_fake() {
+      underlying_map = nullptr;
       in_underlying([this] { initcells(); underlying_map = currentmap; });
       for(hrmap*& m: allmaps) if(m == underlying_map) m = NULL;
       }

goldberg.cpp

@@ -1269,6 +1269,7 @@ EX namespace gp {
       }
 
     hrmap_inverse() {
+      underlying_map = nullptr;
       if(0) {
         println(hlog, "making ucgi");
         dynamicval<eVariation> gva(variation, variation_for(param));

nonisotropic.cpp

@@ -1360,6 +1360,7 @@ EX namespace hybrid {
     cell* gamestart() override { return getCell(underlying_map->gamestart(), 0); }
   
     hrmap_hybrid() {
+      underlying_map = nullptr;
       twisted = false;
       disc_quotient = 0;
       in_underlying([this] { initcells(); underlying_map = currentmap; });