Fix for Footer is missing if fisrt page different header/footer is set

Reviewed on:
	https://gerrit.libreoffice.org/7589

Change-Id: I2a2f2abc0dcf5542b7b950f9a232d7155a055fdd
CppunitTest_sw_ooxmlexport: fix testcase that didn't fail without the fix

Change-Id: I87308b38bb44864db3531366ab354567847b1340