Fix crash when file does not contain header text

Fixes StyleCop/StyleCop#78

Author: citizenmatt

install/StyleCop.nuspec

@@ -3,12 +3,13 @@
   <metadata>
     <id>StyleCop.StyleCop</id>
     <title>StyleCop by JetBrains</title>
-    <version>2016.3.0</version>
+    <version>2016.3.1</version>
     <authors>Matt Ellis, Andy Reeves</authors>
     <owners>JetBrains, Matt Ellis</owners>
     <summary>StyleCop analyzes C# source code to enforce a set of style and consistency rules. Maintained by JetBrains</summary>
     <description>StyleCop analyzes C# source code to enforce a set of style and consistency rules. This plugin is compatible with StyleCop 4.7.54, and maintained by JetBrains.</description>
     <releaseNotes>
+&#8226; Fix crash if the file doesn't have a header (StyleCop/StyleCop#78)
 &#8226; Updated to ReSharper 2016.3
 
 From 2016.2.1:

src/StyleCop.ReSharper/Core/Utils.cs

@@ -662,7 +662,13 @@ public static ITreeNode GetElementAtCaret(ISolution solution, ITextControl textC
         /// </returns>
         public static string GetFileHeader(ICSharpFile file)
         {
-            return GetFileHeaderTreeRange(file).GetDocumentRange().GetText();
+            var documentRange = GetFileHeaderTreeRange(file).GetDocumentRange();
+            if (!documentRange.IsValid())
+            {
+                return string.Empty;
+            }
+
+            return documentRange.GetText();
         }
 
         /// <summary>

src/StyleCop.ReSharper/Properties/AssemblyInfo.cs

@@ -21,8 +21,8 @@
 using System.Runtime.InteropServices;
 using JetBrains.ReSharper.Feature.Services.Daemon;
 
-[assembly: AssemblyTitle("StyleCop R# 8.0.0 Plugin")]
-[assembly: AssemblyDescription("R# plugin for StyleCop")]
+[assembly: AssemblyTitle("StyleCop for ReSharper")]
+[assembly: AssemblyDescription("StyleCop for ReSharper")]
 [assembly: AssemblyConfiguration("")]
 [assembly: AssemblyCompany("")]
 [assembly: AssemblyProduct(StyleCop.Constants.ProductName)]