fix: Fixed missing method exception in Unity 2020.3.15 and older

Author: SolidAlloy

Editor/GenericTypesAnalyzer/GenericTypesAnalyzer.cs

@@ -108,10 +108,15 @@ private static void UpdateGeneratedAssemblies()
 
         private static void FlushConfigChangesToDisk()
         {
+            // AssetDatabase.SaveAssetIfDirty was added in Unity 2020.3.16
+#if UNITY_2020_3_OR_NEWER && ! (UNITY_2020_3_0 || UNITY_2020_3_1 || UNITY_2020_3_2 || UNITY_2020_3_3 || UNITY_2020_3_4 || UNITY_2020_3_5 || UNITY_2020_3_6 || UNITY_2020_3_7 || UNITY_2020_3_8 || UNITY_2020_3_9 || UNITY_2020_3_10 || UNITY_2020_3_11 || UNITY_2020_3_12 || UNITY_2020_3_13 || UNITY_2020_3_14 || UNITY_2020_3_15)
             AssetDatabase.SaveAssetIfDirty(GenerationDatabase<MonoBehaviour>.Instance);
             AssetDatabase.SaveAssetIfDirty(GenerationDatabase<GenericScriptableObject>.Instance);
             AssetDatabase.SaveAssetIfDirty(GenericTypesDatabase<MonoBehaviour>.Instance);
             AssetDatabase.SaveAssetIfDirty(GenericTypesDatabase<GenericScriptableObject>.Instance);
+#else
+            AssetDatabase.SaveAssets();
+#endif
         }
     }
 }