[MC] Remove redundant null check, NFCI (#100928)

`getOrCreateSymbol` should never return a `nullptr`, add an assert and
remove the redundant null check in the if condition.

Author: abhishek-kaushik22

llvm/lib/MC/MCContext.cpp

@@ -697,10 +697,11 @@ MCSectionCOFF *MCContext::getCOFFSection(StringRef Section,
   MCSymbol *COMDATSymbol = nullptr;
   if (!COMDATSymName.empty()) {
     COMDATSymbol = getOrCreateSymbol(COMDATSymName);
+    assert(COMDATSymbol && "COMDATSymbol is null");
     COMDATSymName = COMDATSymbol->getName();
     // A non-associative COMDAT is considered to define the COMDAT symbol. Check
     // the redefinition error.
-    if (Selection != COFF::IMAGE_COMDAT_SELECT_ASSOCIATIVE && COMDATSymbol &&
+    if (Selection != COFF::IMAGE_COMDAT_SELECT_ASSOCIATIVE &&
         COMDATSymbol->isDefined() &&
         (!COMDATSymbol->isInSection() ||
          cast<MCSectionCOFF>(COMDATSymbol->getSection()).getCOMDATSymbol() !=