minimal fix for ime in terminal

node_modules/ace/lib/ace/keyboard/textinput.js

@@ -364,10 +364,11 @@ var TextInput = function(parentNode, host) {
             return;
         // console.log("onCompositionStart", inComposition)
         inComposition = {};
+        inComposition.canUndo = host.session.$undoManager;
         host.onCompositionStart();
         setTimeout(onCompositionUpdate, 0);
         host.on("mousedown", onCompositionEnd);
-        if (!host.selection.isEmpty()) {
+        if (inComposition.canUndo && !host.selection.isEmpty()) {
             host.insert("");
             host.session.markUndoGroup();
             host.selection.clearSelection();
@@ -385,7 +386,8 @@ var TextInput = function(parentNode, host) {
         host.onCompositionUpdate(val);
         if (inComposition.lastValue)
             host.undo();
-        inComposition.lastValue = val;
+        if (inComposition.canUndo)
+            inComposition.lastValue = val;
         if (inComposition.lastValue) {
             var r = host.selection.getRange();
             host.insert(inComposition.lastValue);