fdo#49692 fix RTF export of empty paragraph numbering rules
fdo#49692 fix RTF export of empty paragraph numbering rules

When there is a numbering rule, the fallback text is constructed so that
whitespace separates the numbering and the paragraph text. When the
numbering is empty, we don't need that separator.

Change-Id: I17a11ddd73addc8c95a0c2b54402e6dd2705d094

JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core