Fix for NaN values

Author: amemov

libc/utils/MPFRWrapper/MPCommon.cpp

@@ -78,6 +78,9 @@ MPFRNumber MPFRNumber::acospi() const {
   mpfr_acospi(result.value, value, mpfr_rounding);
   return result;
 #else
+  if (result.is_nan()) {
+    return result;
+  }
   mpfr_acos(result.value, value, mpfr_rounding);
   MPFRNumber value_pi(0.0, 1280);
   mpfr_const_pi(value_pi.value, MPFR_RNDN);