Fix HtmlValidateCli.GetInstalledVersion() method to return null when the package is not installed

Author: YevgeniyShunevych

CHANGELOG.md

@@ -12,6 +12,10 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - Upgrade `Atata.Cli` package to v1.2.0.
 - Upgrade `Atata.Cli.Npm` package to v1.2.0.
 
+## Fixed
+
+- Fix `HtmlValidateCli.GetInstalledVersion()` method to return `null` when the package is not installed.
+
 ## [1.1.0] - 2021-07-13
 
 ### Added

src/Atata.Cli.HtmlValidate/HtmlValidateCli.cs

@@ -82,7 +82,14 @@ private string ReadOutputFromFile(string filePath)
             return File.ReadAllText(fullFilePath);
         }
 
-        public override string GetInstalledVersion() =>
-            Execute("--version").Output.Split('-').Last();
+        /// <inheritdoc cref="GlobalNpmPackageCli{TCli}.GetInstalledVersion"/>
+        public override string GetInstalledVersion()
+        {
+            CliCommandResult versionCommandResult = ExecuteRaw("--version");
+
+            return versionCommandResult.HasError
+                ? null
+                : versionCommandResult.Output.Split('-').Last();
+        }
     }
 }