qbsp: throw exception in ExportLeaf if a leaf bounds is invalid

add check in test suite that qbspfeatures.map doesn't get upgraded to BSP2 due to invalid leaf bounds

qbsp/test_qbsp.cc

@@ -908,6 +908,8 @@ TEST_CASE("features", "[testmaps_q1]")
     const auto [bsp, bspx, prt] = LoadTestmapQ1("qbspfeatures.map");
 
     REQUIRE(prt.has_value());
+
+    CHECK(bsp.loadversion == &bspver_q1);
 }
 
 bool PortalMatcher(const prtfile_winding_t& a, const prtfile_winding_t &b)

qbsp/writebsp.cc

@@ -30,6 +30,7 @@
 #include <common/json.hh>
 #include <fstream>
 
+#include <stdexcept>
 using nlohmann::json;
 
 /**
@@ -156,6 +157,10 @@ static void ExportLeaf(mapentity_t *entity, node_t *node)
 
     dleaf.contents = remapped.native;
 
+    if (node->bounds.maxs()[0] < node->bounds.mins()[0]) {
+        throw std::runtime_error("leaf bounds was unassigned");
+    }
+
     /*
      * write bounding box info
      */