Add regression tests for #2836

They test if it is possible to delete lines from the array that is
mutated by a changeset, and after no line is left insert some
characters (with or without new lines).

Author: webzwo0i

src/node/easysync_tests.js

@@ -222,6 +222,17 @@ function runTests() {
     ['skip', 1, 1, true]
   ], ["banana\n", "cabbage\n", "duffle\n"]);
 
+// #2836 regressions
+  runMutationTest(8, ["\n"], [
+    ['remove', 1, 1, "\n"],
+    ['insert',"c", 0]
+  ], ["c"]);
+  runMutationTest(9, ["\n"], [
+    ['remove', 1, 1, "\n"],
+    ['insert', "a"],
+    ['insert',"c\n", 1]
+  ], ["ac\n"]);
+
   function poolOrArray(attribs) {
     if (attribs.getAttrib) {
       return attribs; // it's already an attrib pool