Fix documentation error and add log for future debuging for QueryBody; Set SolarSystem relative path if a mod adds a .json file to overwrite it. (#926)

<!-- Be sure to reference the existing issue if it exists -->

## Bug fixes

- Added log message in the event the QueryBody could not find a body
- Fixed documentation to match API
- Discovered that if you modify the default SolarySystem, `QuerySystem`
will fail due to an IO error as the relative path is not set. While not
an ideal solution, we have settled on just setting the relativePath if a
mod adjusts the system. This will mean that the last mod loaded that
makes these changes will have set the relative path.

NewHorizons/Main.cs

@@ -694,10 +694,25 @@ namespace NewHorizons
 
             if (SystemDict.ContainsKey(starSystemName))
             {
+                // Both changing the Mod and RelativePath are weird and will likely cause incompat issues if two mods both affected the same system
+                // It's mostly just to fix up the config compared to the default one NH makes for the base StarSystem
+
                 if (SystemDict[starSystemName].Config.GlobalMusic == null && SystemDict[starSystemName].Config.Skybox == null)
+                {
                     SystemDict[starSystemName].Mod = mod;
-                if (SystemDict[starSystemName].Config.extras == null)
+                }
+
+                // If a mod contains a change to the default system, set the relative path.
+                // Warning: If multiple systems make changes to the default system, only the relativePath will be set to the last mod loaded.
+                if (string.IsNullOrEmpty(SystemDict[starSystemName].RelativePath))
+                {
                     SystemDict[starSystemName].RelativePath = relativePath;
+                }
+                else
+                {
+                    NHLogger.LogWarning($"Two (or more) mods are making system changes to {starSystemName} which may result in errors");
+                }
+
                 SystemDict[starSystemName].Config.Merge(starSystemConfig);
             }
             else

NewHorizons/NewHorizonsApi.cs

@@ -143,9 +143,11 @@ namespace NewHorizons
         public object QueryBody(Type outType, string bodyName, string jsonPath)
         {
             var planet = Main.BodyDict[Main.Instance.CurrentStarSystem].Find((b) => b.Config.name == bodyName);
-            return planet == null
+            if (planet == null){
-                ? null
+                NHLogger.LogError($"Could not find planet with body name {bodyName}.");
-                : QueryJson(outType, Path.Combine(planet.Mod.ModHelper.Manifest.ModFolderPath, planet.RelativePath), jsonPath);
+				return null;
+			}
+			return QueryJson(outType, Path.Combine(planet.Mod.ModHelper.Manifest.ModFolderPath, planet.RelativePath), jsonPath);
         }
 
         public T QueryBody<T>(string bodyName, string jsonPath)

docs/src/content/docs/guides/extending-configs.md

@@ -49,7 +49,7 @@ Then, use the `QueryBody` method:
 var api = ModHelper.Interactions.TryGetModApi<INewHorizons>("xen.NewHorizons");
 api.GetBodyLoadedEvent().AddListener((name) => {
     ModHelper.Console.WriteLine($"Body: {name} Loaded!");
-    var data = api.QueryBody<MyCoolExtensionData>("$.extras.myCoolExtensionData", name);
+    var data = api.QueryBody<MyCoolExtensionData>(name, "$.extras.myCoolExtensionData");
     // Makes sure the module is not null
     if (data != null) {
         ModHelper.Console.WriteLine($"myCoolExtensionProperty for {name} is {data.myCoolExtensionProperty}!");