From 01cbb584be17ea3ace4910678c35795e6931e731 Mon Sep 17 00:00:00 2001
From: Tae Won Ha <h@taewon.de>
Date: Tue, 5 Jul 2016 19:00:27 +0200
Subject: [PATCH] Guard against invalid positions

---
 SwiftNeoVim/Grid.swift | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/SwiftNeoVim/Grid.swift b/SwiftNeoVim/Grid.swift
index 2f74ba85..5283c620 100644
--- a/SwiftNeoVim/Grid.swift
+++ b/SwiftNeoVim/Grid.swift
@@ -198,6 +198,10 @@ class Grid: CustomStringConvertible {
   }
 
   func isCellEmpty(position: Position) -> Bool {
+    guard self.isSane(position: position) else {
+      return false
+    }
+
     if self.cells[position.row][position.column].string.characters.count == 0 {
       return true
     }
@@ -241,4 +245,12 @@ class Grid: CustomStringConvertible {
       self.cells[i].replaceRange(region.left...region.right, with: clearedRow)
     }
   }
+
+  private func isSane(position position: Position) -> Bool {
+    guard position.row < self.size.height && position.column < self.size.width else {
+      return false
+    }
+
+    return true
+  }
 }