Handle missing profile stats gracefully instead of asserting.

There is a bug souffle-lang#2426, which causes an assertion in the
SelingerProfileSipsMetric::getReordering. There is no need to assert,
since we can handle the problem gracefully by not reordering atoms.

src/ast2ram/utility/SipsMetric.cpp

@@ -131,7 +131,12 @@ std::vector<std::size_t> SelingerProfileSipsMetric::getReordering(
     auto sccAtoms = filter(ast::getBodyLiterals<ast::Atom>(*clause),
             [&](auto* atom) { return contains(sccRelations, program.getRelation(*atom)); });
 
-    assert(profileUseAnalysis->hasAutoSchedulerStats() && "Must have stats in order to auto-schedule!");
+    if (!profileUseAnalysis->hasAutoSchedulerStats()) {
+        std::vector<std::size_t> res;
+        res.resize(atoms.size());
+        std::iota(res.begin(), res.end(), 0);
+        return res;
+    }
 
     auto* prof = profileUseAnalysis;
     auto getJoinSize = [&prof](bool isRecursive, const std::string& rel, std::set<std::size_t> joinKeys,