Fix typo

Change-Id: I1a657bd08ff7a6108a20d57d5ebe9f104fcbe3fd
Reviewed-on: https://gerrit.libreoffice.org/73420
Tested-by: Jenkins
Reviewed-by: Julien Nabet <serval2412@yahoo.fr>

forms/source/xforms/propertysetbase.hxx

@@ -240,7 +240,7 @@ protected:
         any notifications if the "current value" is also <FALSE/> - which might be wrong, since
         the guessing of the "old value" differed from the real initial value which was <TRUE/>.
 
-        Too confusing? Okay, than just call this method for every property you have.
+        Too confusing? Okay, then just call this method for every property you have.
 
         @param nHandle
             the handle of the property. Must denote a property supported by this instance, i.e.