fix MSI version parsing (#5475)

build.psm1

@@ -1904,7 +1904,15 @@ function Get-PackageVersionAsMajorMinorBuildRevision
     } elseif (1 -lt $packageVersionTokens.Count) {
         # We have all the four fields
         $packageBuildTokens = ([regex]::Matches($packageVersionTokens[1], "\d+"))[0].value
-        $packageVersion = $packageVersion + '.' + $packageBuildTokens
+
+        if ($packageBuildTokens)
+        {
+            $packageVersion = $packageVersion + '.' + $packageBuildTokens
+        }
+        else
+        {
+            $packageVersion = $packageVersion
+        }
     }
 
     $packageVersion