Avoided crashes when generating code corresponding to translation units at invalid locations.

Signed-off-by: Dimitar Dobrev <dpldobrev@yahoo.com>

src/AST/TranslationUnit.cs

@@ -38,6 +38,8 @@ namespace CppSharp.AST
 
         public bool IsSystemHeader { get; set; }
 
+        public bool IsValid { get { return FilePath != "<invalid>"; } }
+
         /// Contains the path to the file.
         public string FilePath;
 

src/Generator/Driver.cs

@@ -312,7 +312,7 @@ namespace CppSharp
             if (!Directory.Exists(outputPath))
                 Directory.CreateDirectory(outputPath);
 
-            foreach (var output in outputs)
+            foreach (var output in outputs.Where(o => o.TranslationUnit.IsValid))
             {
                 var fileBase = output.TranslationUnit.FileNameWithoutExtension;