try-catch registry lookup to avoid crashes on non-windows platforms

osu.Game.Tournament/IPC/FileBasedIPC.cs

@@ -238,6 +238,8 @@ namespace osu.Game.Tournament.IPC
         {
             Logger.Log("Trying to find stable in registry");
 
+            try
+            {
                 string stableInstallPath;
 
                 using (RegistryKey key = Registry.ClassesRoot.OpenSubKey("osu"))
@@ -245,6 +247,10 @@ namespace osu.Game.Tournament.IPC
 
                 if (ipcFileExistsInDirectory(stableInstallPath))
                     return stableInstallPath;
+            }
+            catch
+            {
+            }
 
             return null;
         }