Fix crash on startup by providing a migration path for DefaultTerminalPath property (#996)

* Provide a migration path for DefaultTerminalPath property, preventing access when null

* Increment Version Number to v0.10.1

Author: lukeblevins

Files.Package/Package.appxmanifest

@@ -9,7 +9,7 @@
          xmlns:uap4="http://schemas.microsoft.com/appx/manifest/uap/windows10/4"
          xmlns:uap5="http://schemas.microsoft.com/appx/manifest/uap/windows10/5" 
          IgnorableNamespaces="uap uap5 mp rescap desktop4 desktop">
-	<Identity Name="FilesUWPDev" Publisher="CN=53EC4384-7F5B-4CF6-8C23-513FFE9D1AB7" Version="0.10.0.0" />
+	<Identity Name="FilesUWPDev" Publisher="CN=53EC4384-7F5B-4CF6-8C23-513FFE9D1AB7" Version="0.10.1.0" />
 	<Properties>
 		<DisplayName>Files UWP - Dev</DisplayName>
 		<PublisherDisplayName>Yair A</PublisherDisplayName>

Files/DataModels/TerminalFileModel.cs

@@ -50,7 +50,11 @@ public async Task<bool> AddOrRemoveTerminal(TerminalModel terminal, string packa
             }
             else if (!isInstalled)
             {
-                if (DefaultTerminalPath.Equals(terminal.Path, StringComparison.OrdinalIgnoreCase))
+                if (string.IsNullOrWhiteSpace(DefaultTerminalPath))
+                {
+                    ResetToDefaultTerminal();
+                }
+                else if (DefaultTerminalPath.Equals(terminal.Path, StringComparison.OrdinalIgnoreCase))
                 {
                     ResetToDefaultTerminal();
                 }