Don't throw if texture is null, it spams the console needlessly

Textures are getting disposed from under us, and if we try to
use them in the project window, the console gets filled with
exceptions that are useless to the user. Catch and return in
these cases.

src/UnityExtension/Assets/Editor/GitHub.Unity/UI/ProjectWindowInterface.cs

@@ -215,7 +215,14 @@ namespace GitHub.Unity
             }
 
             var status = index >= 0 ? entries[index].Status : GitFileStatus.None;
-            var texture = Styles.GetFileStatusIcon(status, indexLock >= 0);
+            var isLocked = indexLock >= 0;
+            var texture = Styles.GetFileStatusIcon(status, isLocked);
+
+            if (texture == null)
+            {
+                logger.Warning("Unable to retrieve texture for Status: {0} IsLocked:{1}", isLocked);
+                return;
+            }
 
             Rect rect;