iphone - Error #2007: Parameter child must be non-null -

having nothing errors today! sooo nice bit of one.

i calling external child swfs air app; super simple - calling them button, , removing them "home" button, that's it. these errors , cannot publish, test, without crashing entire system. please help! have been stuck on this, literally, weeks!

this error:

typeerror: error #2007: parameter child must non-null. @ flash.display::displayobjectcontainer/removechild() @ pocketdinos_fla::maintimeline/fl_clicktogotoandstopatframe_20_1()   [pocketdinos_fla.maintimeline::frame162:18] test movie terminated. 

and assume causing problem on main timeline (this code on main timeline):

 stop();  //home button  button_home.addeventlistener(mouseevent.click, fl_clicktoloadunloadswf_01_1,false,0,true);  function fl_clicktoloadunloadswf_01_1(event:mouseevent):void { removechild(fl_proloader_01); fl_proloader_01.unloadandstop(); fl_proloader_01 = null; }  button_home.addeventlistener(mouseevent.click,      fl_clicktogotoandstopatframe_01_1,false,0,true);  function fl_clicktogotoandstopatframe_01_1(event:mouseevent):void { removechild(fl_proloader_01);  } button_home.addeventlistener(mouseevent.click, fl_clicktostopallsounds_01_1,false,0,true);  function fl_clicktostopallsounds_01_1(event:mouseevent):void { soundmixer.stopall(); }  button_home.addeventlistener(mouseevent.click,      fl_clicktogotoandstopatframe_01_2,false,0,true);  function fl_clicktogotoandstopatframe_01_2(event:mouseevent):void { gotoandstop("home"); }  //back time period button  back_to_triassic.addeventlistener(mouseevent.click,     fl_clicktoloadunloadswf_01_2,false,0,true);  function fl_clicktoloadunloadswf_01_2(event:mouseevent):void { removechild(fl_proloader_01); fl_proloader_01.unloadandstop(); fl_proloader_01 = null; }  back_to_triassic.addeventlistener(mouseevent.click,    fl_clicktogotoandstopatframe_01_3,false,0,true);  function fl_clicktogotoandstopatframe_01_3(event:mouseevent):void { removechild(fl_proloader_01);  } back_to_triassic.addeventlistener(mouseevent.click,     fl_clicktostopallsounds_01_2,false,0,true);  function fl_clicktostopallsounds_01_2(event:mouseevent):void { soundmixer.stopall(); }  back_to_triassic.addeventlistener(mouseevent.click,     fl_clicktogotoandstopatframe_01_4,false,0,true);  function fl_clicktogotoandstopatframe_01_4(event:mouseevent):void { gotoandstop("tri_home"); }   //start button  start_button_tri_coelophysis.addeventlistener(mouseevent.click,    fl_clicktoloadunloadswf_01_3,false,0,true);  import fl.display.proloader; import flash.events.event;  var fl_proloader_01:proloader;  function fl_clicktoloadunloadswf_01_3(event:mouseevent):void { if(fl_toload_01) {     fl_proloader_01 = new proloader();     fl_proloader_01.load(new urlrequest("dinofilms/triassic_coelophysis.swf"));  fl_proloader_01.contentloaderinfo.addeventlistener(event.complete,oncomplete_01)     addchild(fl_proloader_01);     fl_proloader_01.x = 0;     fl_proloader_01.y = 144; } else {     if(fl_proloader_01!=null) {         removechild(fl_proloader_01);         fl_proloader_01.unloadandstop();         fl_proloader_01 = null;     } } fl_toload_01 = !fl_toload_01;  }  function oncomplete_01(e:event):void { e.currenttarget.content.addeventlistener(event.enter_frame,oef_01); }  function oef_01(e:event):void { if(e.currenttarget.currentframe==e.currenttarget.totalframes) {     e.currenttarget.stop();     e.currenttarget.removeeventlistener(event.enter_frame,oef_01);      removechild(fl_proloader_01);     fl_proloader_01.unloadandstop();     fl_proloader_01 = null; } } 

in function fl_clicktogotoandstopatframe_01_1 removechild(fl_proloader_01); call in function fl_clicktoloadunloadswf_01_1. both functions assigned same movieclip/button, give error null, on line 18 call removechild on same movieclip/button again.