[AddressLowering] NFC: Moved assert above NPE.

Moved the assert that the value which opens an archetype exists before
the call to get its defining instruction which would be an NPE if the
value were in fact null.

Author: nate-chandler

lib/SILOptimizer/Mandatory/AddressLowering.cpp

@@ -1360,8 +1360,8 @@ SILInstruction *AddressLoweringState::getLatestOpeningInst(SILType ty) const {
       auto openingVal =
           getModule()->getRootLocalArchetypeDef(openedTy, function);
 
-      auto *openingInst = openingVal->getDefiningInstruction();
       assert(openingVal && "all opened archetypes should be resolved");
+      auto *openingInst = openingVal->getDefiningInstruction();
       if (latestOpeningInst) {
         if (domInfo->dominates(openingInst, latestOpeningInst))
           return;