cppcheck: fix arrayIndexThenCheck in vcl

Change-Id: Id7258dd35c131c2c8151bc5e0f97076241e6d10f
Reviewed-on: https://gerrit.libreoffice.org/3868Reviewed-by: Norbert Thiebaud <nthiebaud@gmail.com>
Tested-by: Norbert Thiebaud <nthiebaud@gmail.com>

vcl/source/control/field.cxx

@@ -201,7 +201,7 @@ static bool ImplNumericGetValue( const OUString& rStr, sal_Int64& rValue,
     {
         // check if string is equivalent to zero
         sal_Int16 nIndex = bNegative ? 1 : 0;
-        while( aStr[nIndex] == '0' && nIndex < aStr.getLength() )
+        while (nIndex < aStr.getLength() && aStr[nIndex] == '0')
             ++nIndex;
         if( nIndex < aStr.getLength() )
         {