allow saving a page with empty text
allow saving a page with empty text

by checking "if text is None" instead of "if not text"

http://lists.wikimedia.org/pipermail/pywikipedia-l/2014-May/008740.html

Change-Id: I26426394ae4844a029c5867446d481d53faae68d

Darkdadaah/pywikibot-core,xZise/pywikibot-core,h4ck3rm1k3/pywikibot-core,VcamX/pywikibot-core,h4ck3rm1k3/pywikibot-core,hasteur/g13bot_tools_new,magul/pywikibot-core,hasteur/g13bot_tools_new,PersianWikipedia/pywikibot-core,emijrp/pywikibot-core,darthbhyrava/pywikibot-local,npdoty/pywikibot,TridevGuha/pywikibot-core,magul/pywikibot-core,hasteur/g13bot_tools_new,wikimedia/pywikibot-core,Darkdadaah/pywikibot-core,icyflame/batman,wikimedia/pywikibot-core,happy5214/pywikibot-core,jayvdb/pywikibot-core,smalyshev/pywikibot-core,jayvdb/pywikibot-core,happy5214/pywikibot-core,npdoty/pywikibot,valhallasw/pywikibot-core,trishnaguha/pywikibot-core