fix +8094 Pane/tab & navigation errors

package.json

@@ -81,7 +81,7 @@
         "c9.ide.ace.split": "#0ae0151c78",
         "c9.ide.ace.statusbar": "#d95be89d53",
         "c9.ide.ace.stripws": "#cf0f42ac59",
-        "c9.ide.behaviors": "#6aad7006a0",
+        "c9.ide.behaviors": "#c3a9402cde",
         "c9.ide.closeconfirmation": "#a28bfd8272",
         "c9.ide.configuration": "#adf50fdaa2",
         "c9.ide.dialog.wizard": "#7667ec79a8",

plugins/c9.ide.editors/pane.js

@@ -230,7 +230,7 @@ define(function(require, module, exports) {
             }
             
             function hsplit(far, vertically, split, ignore) {
-                if (!split || !split.parentNode) split = amlPane;
+                if (!$isValidSplit(split) || !split.parentNode) split = amlPane;
                 
                 queue = []; // Used for resizing later
                 
@@ -270,6 +270,16 @@ define(function(require, module, exports) {
                 return newtab.cloud9pane;
             }
             
+            function $isValidSplit(container) {
+                // would be better to use tabmanager.containers instead
+                while (container) {
+                    if (container.localName == "bar")
+                        break;
+                    container = container.parentNode;
+                }
+                return !!container;
+            }
+            
             // Resize all editors in the queue
             function resizeAll(){
                 queue.forEach(function(node) {
@@ -399,6 +409,8 @@ define(function(require, module, exports) {
                 }
                 
                 if (next) {
+                    if (!$isValidSplit(next)) 
+                        return;
                     // Moving from horizontal to vertical or vice verse
                     if (force || next.parentNode.localName != amlPane.parentNode.localName) {
                         var tosplit = force || next.parentNode.localName == "bar"