MdeModulePkg: Add NULL pointer check for RegularExpressionDxe.

Refine code by adding NULL pointer check to avoid potential NULL pointer dereferenced.

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Qiu Shumin <shumin.qiu@intel.com>
Reviewed-by: Samer El-Haj-Mahmoud <elhaj@hpe.com>

git-svn-id: https://svn.code.sf.net/p/edk2/code/trunk/edk2@19271 6f19259b-4bc3-4df7-8a09-765794883524

MdeModulePkg/Universal/RegularExpressionDxe/Oniguruma/regexec.c

@@ -243,7 +243,9 @@ onig_region_new(void)
   OnigRegion* r;
 
   r = (OnigRegion* )xmalloc(sizeof(OnigRegion));
-  onig_region_init(r);
+  if (r != NULL) {
+    onig_region_init(r);
+  }
   return r;
 }
 
@@ -284,6 +286,10 @@ onig_region_copy(OnigRegion* to, OnigRegion* from)
     to->allocated = from->num_regs;
   }
 
+  if (to->beg == NULL || to->end == NULL) {
+    return;
+  }
+
   for (i = 0; i < from->num_regs; i++) {
     to->beg[i] = from->beg[i];
     to->end[i] = from->end[i];