diff --git a/LICENSE b/LICENSE
new file mode 100644
index 0000000..9e21a7e
--- /dev/null
+++ b/LICENSE
@@ -0,0 +1,21 @@
+
+
+Copyright (c) 2016-2018, The Cytoscape Consortium.
+
+Permission is hereby granted, free of charge, to any person obtaining a copy of
+this software and associated documentation files (the “Software”), to deal in
+the Software without restriction, including without limitation the rights to
+use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies
+of the Software, and to permit persons to whom the Software is furnished to do
+so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED “AS IS”, WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.
\ No newline at end of file
diff --git a/cytoscape-navigator.js b/cytoscape-navigator.js
index 3b9c05c..03b483d 100644
--- a/cytoscape-navigator.js
+++ b/cytoscape-navigator.js
@@ -597,8 +597,12 @@
           var targetOffset = $(ev.target).offset()
             , overlayOffset = that.$overlay.offset()
 
-          ev.offsetX = ev.offsetX - overlayOffset.left + targetOffset.left
-          ev.offsetY = ev.offsetY - overlayOffset.top + targetOffset.top
+          if(targetOffset && overlayOffset){
+            ev.offsetX = ev.offsetX - overlayOffset.left + targetOffset.left
+            ev.offsetY = ev.offsetY - overlayOffset.top + targetOffset.top
+          } else {
+            return false;
+          }
         }
 
         if (ev.type == 'mousemove' || ev.type == 'touchmove') {