Fixed an index out of range if the AbstractLineList reported wrong index lines

Author: danipen

src/TextMateSharp/Model/AbstractLineList.cs

@@ -22,18 +22,27 @@ public void SetModel(TMModel model)
 
         public void AddLine(int line)
         {
-            this.list.Insert(line, new ModelLine());
+            lock (mLock)
+            {
+                this.list.Insert(line, new ModelLine());
+            }
         }
 
         public void RemoveLine(int line)
         {
-            this.list.RemoveAt(line);
+            lock (mLock)
+            {
+                this.list.RemoveAt(line);
+            }
         }
 
         public ModelLine Get(int index)
         {
             lock (mLock)
             {
+                if (index < 0 || index >= this.list.Count)
+                    return null;
+
                 return this.list[index];
             }
         }

src/TextMateSharp/Model/TMModel.cs

@@ -94,7 +94,9 @@ void ThreadWorker()
                         continue;
                     }
 
-                    if (model.lines.Get(toProcess).IsInvalid)
+                    var modelLine = model.lines.Get(toProcess);
+
+                    if (modelLine != null && modelLine.IsInvalid)
                     {
                         try
                         {