From 24cbb23622e30f2a3c35b7ee69192d677e1e2dae Mon Sep 17 00:00:00 2001
From: jahorton <jahorton@sil.org>
Date: Thu, 11 Mar 2021 10:51:48 +0700
Subject: [PATCH] fix(common/models): prevents "undefined" reversion display
 string

---
 common/predictive-text/worker/model-compositor.ts | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/common/predictive-text/worker/model-compositor.ts b/common/predictive-text/worker/model-compositor.ts
index 3b05b9ad28..97199b3383 100644
--- a/common/predictive-text/worker/model-compositor.ts
+++ b/common/predictive-text/worker/model-compositor.ts
@@ -487,7 +487,11 @@ class ModelCompositor {
     let postContextTokenization = this.tokenize(postContext);
     if(postContextTokenization) {
       // Handles display string for reversions triggered by accepting a suggestion mid-token.
-      revertedPrefix = postContextTokenization.left[postContextTokenization.left.length-1];
+      if(postContextTokenization.left.length > 0) {
+        revertedPrefix = postContextTokenization.left[postContextTokenization.left.length-1];
+      } else {
+        revertedPrefix = '';
+      }
       revertedPrefix += postContextTokenization.caretSplitsToken ? postContextTokenization.right[0] : '';
     } else {
       revertedPrefix = this.wordbreak(postContext);