tdf#92648 fix DOCX import regression (textbox shrinking in footers)

caused by the fix for tdf#91260

(cherry picked from commit 16331514)

Change-Id: I4a5a27b51c4cb1304647b5432c06ca9c5a96590d
Reviewed-on: https://gerrit.libreoffice.org/19877Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Miklos Vajna <vmiklos@collabora.co.uk>

sw/source/core/objectpositioning/anchoredobjectposition.cxx

@@ -484,8 +484,10 @@ SwTwips SwAnchoredObjectPosition::_ImplAdjustVertRelPos( const SwTwips nTopOfAnc
                 SwFrameFormat* pFrameFormat = ::FindFrameFormat(&GetObject());
                 SwFormatFrmSize aSize(pFormat->GetFrmSize());
                 SwTwips nShrinked = aSize.GetHeight() - (nProposedRelPosY - nAdjustedRelPosY);
-                aSize.SetHeight( nShrinked > 0 ? nShrinked : 0 );
-                pFrameFormat->SetFormatAttr(aSize);
+                if (nShrinked >= 0) {
+                    aSize.SetHeight( nShrinked );
+                    pFrameFormat->SetFormatAttr(aSize);
+                }
                 nAdjustedRelPosY = nProposedRelPosY;
             } else if ( SwTextBoxHelper::findTextBox(pFormat) )
                 // when the shape has a textbox, use only the proposed vertical position