MdeModulePkg/DxeCore: Fix ASSERT() from GCD DEBUG() messages

MdeModulePkg/DxeCore: Fix ASSERT() from GCD DEBUG() messages

If a BaseAddress of NULL is passed into DXE Core services
CoreAllocateIoSpace() or CoreAllocateMemorySpace(), and
DEBUG() messages are enabled, then a NULL pointer reference
is made.  The parameter check for BaseAddress is performed
in the function CoreAllocateSpace() after the DEBUG()
messages.  A check is added in the DEBUG() messages to
prevent the NULL pointer reference.

This issue was found with PI SCTs with DEBUG messages
enabled in the DXE Core.

Cc: Feng Tian <feng.tian@intel.com>
Cc: Star Zeng <star.zeng@intel.com>
Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Michael Kinney <michael.d.kinney@intel.com>
Reviewed-by: Star Zeng <star.zeng@intel.com>
Reviewed-by: Feng Tian <feng.tian@Intel.com>
Reviewed-by: Liming Gao <liming.gao@intel.com>