cid#1357164 correct CovertyScan possible DIVIDE_BY_ZERO

Also covers cid#1357165, exclude possibility that value equals
zero at the same place negative values get excluded

Change-Id: If3fd6143fb13f0d29f5fba304f9f337f7a7aa74c
Reviewed-on: https://gerrit.libreoffice.org/23592Reviewed-by: Armin Le Grand <Armin.Le.Grand@cib.de>
Tested-by: Armin Le Grand <Armin.Le.Grand@cib.de>

sd/source/ui/view/drviewsh.cxx

@@ -120,7 +120,7 @@ void DrawViewShell::MakeVisible(const Rectangle& rRect, vcl::Window& rWin)
                 nFreeSpaceX = rRect.GetWidth();
             }
 
-            if(nFreeSpaceX < 0)
+            if(nFreeSpaceX <= 0)
             {
                 SAL_WARN("sd", "The given Rectangle contains values that lead to numerical overflows (!)");
             }
@@ -165,7 +165,7 @@ void DrawViewShell::MakeVisible(const Rectangle& rRect, vcl::Window& rWin)
                 nFreeSpaceY = rRect.GetHeight();
             }
 
-            if(nFreeSpaceY < 0)
+            if(nFreeSpaceY <= 0)
             {
                 SAL_WARN("sd", "The given Rectangle contains values that lead to numerical overflows (!)");
             }