Refine lobby map generation logic

In early iterations of the lobby map generation logic, a for loop was
used to retry map generation with alternative seeds in case it
failed. This seed randomization logic didn't exist in the final merged
version, but the for loop wasn't cleanup up, and ends up repeating any
map generation failures 5 times deterministically.

Additionally, the logic caught Exception instead of the more specific
MapGenerationException, which is the only exception that is expected
to arise in healthy builds/configurations (due to bad luck rather than
bugs).

This change:

- removes the for loop;

- only catches MapGenerationException;

- adjusts the user-visible failure message to reflect that trying
  again (without adjusting settings) is a valid course of action (now
  that it's not done internally);

OpenRA.Mods.Common/Widgets/Logic/MapGeneratorLogic.cs

@@ -392,33 +392,27 @@ namespace OpenRA.Mods.Common.Widgets.Logic
 			preview.Clear();
 			Task.Run(() =>
 			{
-				for (var i = 0; i < 5; i++)
+				try
 				{
-					try
-					{
-						var args = settings.Compile(selectedTerrain, size);
-						var map = generator.Generate(modData, args);
+					var args = settings.Compile(selectedTerrain, size);
+					var map = generator.Generate(modData, args);
 
-						// Map UID and preview image are generated on save
-						map.Save(package);
-						args.Uid = map.Uid;
+					// Map UID and preview image are generated on save
+					map.Save(package);
+					args.Uid = map.Uid;
 
-						Game.RunAfterTick(() =>
-						{
-							preview.Update(map);
-							onGenerate(args, package);
-							generating = false;
-						});
-						return;
-					}
-					catch (Exception)
+					Game.RunAfterTick(() =>
 					{
-						// Ignore the exception
-					}
+						preview.Update(map);
+						onGenerate(args, package);
+						generating = false;
+					});
+				}
+				catch (MapGenerationException)
+				{
+					failed = true;
+					generating = false;
 				}
-
-				failed = true;
-				generating = false;
 			});
 		}
 

mods/cnc/fluent/chrome.ftl

@@ -540,7 +540,7 @@ label-mapchooser-random-map-error = Map Generation Failed
 button-mapchooser-random-map-generate = Generate
 label-mapchooser-random-map-tileset = Environment:
 label-mapchooser-random-map-size = Map Size:
-label-mapchooser-random-map-error-desc = Adjust the settings to try again.
+label-mapchooser-random-map-error-desc = Adjust the settings or try again.
 
 ## missionbrowser.yaml
 button-missionbrowser-panel-mission-info = Mission Info

mods/common/fluent/chrome.ftl

@@ -359,7 +359,7 @@ label-mapchooser-random-map-error = Map Generation Failed
 button-mapchooser-random-map-generate = Generate
 label-mapchooser-random-map-tileset = Environment:
 label-mapchooser-random-map-size = Map Size:
-label-mapchooser-random-map-error-desc = Adjust the settings to try again.
+label-mapchooser-random-map-error-desc = Adjust the settings or try again.
 
 ## missionbrowser.yaml
 button-missionbrowser-panel-start-briefing-video = Watch Briefing