Bug 1276465 - Check if autompleter map item exists before using it. r=bgrins

MozReview-Commit-ID: JqOnT1tT4rS

--HG--
extra : transplant_source : %02%3E%3F/%F3%CF%15%15%BFM%3FX%A2U%07%D7%9D-b%B6

devtools/client/sourceeditor/autocomplete.js

@@ -381,9 +381,11 @@ function getPopup({ ed }) {
  * implementation of completer supports it.
  */
 function getInfoAt({ ed }, caret) {
-  let completer = autocompleteMap.get(ed).completer;
-  if (completer && completer.getInfoAt) {
-    return completer.getInfoAt(ed.getText(), caret);
+  if (autocompleteMap.has(ed)) {
+    let completer = autocompleteMap.get(ed).completer;
+    if (completer && completer.getInfoAt) {
+      return completer.getInfoAt(ed.getText(), caret);
+    }
   }
 
   return null;