Add nullability to large parts of the codebase

tests/LibraryTests/SpeciesTest.cpp

@@ -6,9 +6,11 @@
 using namespace CreatureLib::Library;
 
 TEST_CASE("Set Variant") {
-    auto defaultVariant = new SpeciesVariant("default", 0, 0, 0, {0, 1}, StatisticSet<u16>(), {}, {}, nullptr);
+    auto defaultVariant =
+        new SpeciesVariant("default", 0, 0, 0, {0, 1}, StatisticSet<u16>(), {}, {}, new LearnableAttacks(0));
     auto c = CreatureSpecies(0, "foo", defaultVariant, 0, "", 0);
-    auto secondVariant = new SpeciesVariant("second", 0, 0, 0, {0, 1}, StatisticSet<u16>(), {}, {}, nullptr);
+    auto secondVariant =
+        new SpeciesVariant("second", 0, 0, 0, {0, 1}, StatisticSet<u16>(), {}, {}, new LearnableAttacks(0));
     c.SetVariant("second"_cnc, secondVariant);
 }