MdeModulePkg: SectionExtractionPei cumulative codeql issues.

Running Codeql on MdeModulePkg/Universal/SectionExtractionPei drivers results
in codeql errors stemming from missing null tests.

Signed-off-by: Aaron Pop <aaronpop@microsoft.com>

Co-authored-by: Michael Kubacki <michael.kubacki@microsoft.com>
Co-authored-by: Taylor Beebe <tabeebe@microsoft.com>
Co-authored-by: pohanch <125842322+pohanch@users.noreply.github.com>
Co-authored-by: kenlautner <85201046+kenlautner@users.noreply.github.com>
Co-authored-by: Oliver Smith-Denny <osde@linux.microsoft.com>
Co-authored-by: Sean Brogan <sean.brogan@microsoft.com>
Co-authored-by: Aaron <aaronpop@microsoft>

Author: 7 people

MdeModulePkg/Universal/SectionExtractionPei/SectionExtractionPei.c

@@ -251,12 +251,15 @@ SectionExtractionPeiEntry (
   if (ExtractHandlerNumber > 0) {
     GuidPpi = (EFI_PEI_PPI_DESCRIPTOR *)AllocatePool (ExtractHandlerNumber * sizeof (EFI_PEI_PPI_DESCRIPTOR));
     ASSERT (GuidPpi != NULL);
-    while (ExtractHandlerNumber-- > 0) {
-      GuidPpi->Flags = EFI_PEI_PPI_DESCRIPTOR_PPI | EFI_PEI_PPI_DESCRIPTOR_TERMINATE_LIST;
-      GuidPpi->Ppi   = (VOID *)&mCustomGuidedSectionExtractionPpi;
-      GuidPpi->Guid  = &ExtractHandlerGuidTable[ExtractHandlerNumber];
-      Status         = PeiServicesInstallPpi (GuidPpi++);
-      ASSERT_EFI_ERROR (Status);
+
+    if (GuidPpi != NULL) {
+      while (ExtractHandlerNumber-- > 0) {
+        GuidPpi->Flags = EFI_PEI_PPI_DESCRIPTOR_PPI | EFI_PEI_PPI_DESCRIPTOR_TERMINATE_LIST;
+        GuidPpi->Ppi   = (VOID *)&mCustomGuidedSectionExtractionPpi;
+        GuidPpi->Guid  = &ExtractHandlerGuidTable[ExtractHandlerNumber];
+        Status         = PeiServicesInstallPpi (GuidPpi++);
+        ASSERT_EFI_ERROR (Status);
+      }
     }
   }