approxEqual: check isFinite()

Necessary as all comparisons involving a Nan evaluate to false and the
assert() in isRepresentableInteger() was hit by crash test documents
where approxEqual() was called with a least one Nan.

Change-Id: I9e8f41c36c0cf14cabf47c3df773c601d32682d6

sal/rtl/math.cxx

@@ -1095,6 +1095,8 @@ bool SAL_CALL rtl_math_approxEqual(double a, double b) SAL_THROW_EXTERN_C()
     if (a == 0.0 || b == 0.0)
         return false;
     const double d = fabs(a - b);
+    if (!rtl::math::isFinite(d))
+        return false;   // Nan or Inf involved
     if (d > ((a = fabs(a)) * e44) || d > ((b = fabs(b)) * e44))
         return false;
     if (isRepresentableInteger(d) && isRepresentableInteger(a) && isRepresentableInteger(b))