forcepoint #14 check to see if we incremented at all

Change-Id: Ia4670adbddcc8501cf522be296b3061a3529f880
Reviewed-on: https://gerrit.libreoffice.org/50607Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Michael Stahl <mstahl@redhat.com>
(cherry picked from commit 31deb001)

vcl/source/helper/strhelper.cxx

@@ -300,9 +300,12 @@ OUString WhitespaceToSpace( const OUString& rLine, bool bProtect )
     *pLeap = 0;
 
     // there might be a space at beginning or end
-    pLeap--;
-    if( *pLeap == ' ' )
-        *pLeap = 0;
+    if (pLeap > pBuffer)
+    {
+        pLeap--;
+        if( *pLeap == ' ' )
+            *pLeap = 0;
+    }
 
     return OUString(*pBuffer == ' ' ? pBuffer+1 : pBuffer);
 }