[SYCL] Initialize error code in sycl::exception (#12256)

If there is no backend specific error code associated with the
sycl::exception then error code must be 0, so initialize with 0 by
default, otherwise static analyzer complains about unitialized data
member.

Author: againull

sycl/include/sycl/exception.hpp

@@ -105,7 +105,7 @@ class __SYCL_EXPORT exception : public virtual std::exception {
   // Exceptions must be noexcept copy constructible, so cannot use std::string
   // directly.
   std::shared_ptr<std::string> MMsg;
-  pi_int32 MPIErr;
+  pi_int32 MPIErr = 0;
   std::shared_ptr<context> MContext;
   std::error_code MErrC = make_error_code(sycl::errc::invalid);