Fix empty combo serialization and update README

Author: saulm314

README.md

@@ -1,5 +1,8 @@
 # https://popruns.github.io/
 # Build
-To build and test the site locally, open the root directory in a terminal and run `python3 build.py`. Requires Python 3+ and .NET SDK 9+.
+To build and test the site locally, open the root directory in a terminal and run `python3 build.py`, then open http://127.0.0.1:8080 in a browser. Hit `Ctrl+C` in the terminal to stop testing. Requires Python 3+ and .NET SDK 9+.
 
-To test just the raw HTML/CSS/JS pages locally, open the root directory in a terminal and run `python3 -m http.server`. Requires Python 3+.
+To test just the raw HTML/CSS/JS pages locally (no Blazor), open the root directory in a terminal and run `python3 -m http.server`, then open http://127.0.0.1:8000 in a browser. Hit `Ctrl+C` in the terminal to stop testing. Requires Python 3+.
+
+## For Novices
+Before testing the site locally, first you need to clone/download the repository, and then open the repository's root directory in a terminal. E.g. in Windows you can do this by navigating to the root directory in file explorer, then right-clicking on any empty space, and pressing "Open in Terminal". Alternatively (in any operating system), open the "Terminal" app, then type `cd path/to/repository` and replace `path/to/repository` with the path for where you cloned/downloaded the repository, e.g. `cd C:\Users\JohnSmith\Documents\github\popruns.github.io`.

blazor/PoprunsBlazorPages/Pages/pop-2008/combo-generator/Generator.cs

@@ -87,7 +87,7 @@ private static string Serialize(IEnumerable<MultiCombo> multiComboStream)
             }
             builder.Append(' ');
         }
-        while (char.IsWhiteSpace(builder[^1]))
+        while (builder.Length > 0 && char.IsWhiteSpace(builder[^1]))
             builder.Remove(builder.Length - 1, 1);
         return builder.ToString();
     }