Update act2model.json

The bug is fixed.The second atom is restored to its earlier position when reshown and does not disturb the first atom when hidden.However I have used a very crude method of storing the position parameters of the second atom.I stored them in velocity of the first atom as it didn't create any problem.the fix can be improved by using global variables to store the position parameter.

Author: prasht63

act2model.json

@@ -36,18 +36,19 @@
   ],
   "propertiesToRetain": [],
   "parameters": [
-    {
+    {   
       "name": "show-second-atom",
       "initialValue": false,
       "onChange": [
         "if (value) {",
         "  addAtom({ element:2,",
-        "                 x: 1.34,",
-        "                 y: 1.23,",
+        "                 x: getAtomProperties(0).vx,",
+        "                 y: getAtomProperties(0).vy,",
         "                 charge:2,",
         "                 vx: 0,",
         "                 vy: 0});",
-        "} else {",
+        "} else {","setAtomProperties(0,{vx:getAtomProperties(1).x , vy:getAtomProperties(1).y});",
+                  
         "  removeAtom(1);",
         "}"
       ]