Fix findTransitiveUsesForAddress when foundUses vector is nullptr

The api should not behave differently when foundUses is nullptr.
The only difference should be in populating it.

No tests. Found by code inspection.

Author: meg-gupta

lib/SIL/Utils/OwnershipUtils.cpp

@@ -1065,14 +1065,12 @@ swift::findTransitiveUsesForAddress(SILValue projectedAddress,
 
     // If we have a load_borrow, add it's end scope to the liveness requirement.
     if (auto *lbi = dyn_cast<LoadBorrowInst>(user)) {
-      if (foundUses) {
-        // FIXME: if we can assume complete lifetimes, then this should be
-        // as simple as:
-        //   for (Operand *use : lbi->getUses()) {
-        //     if (use->endsLocalBorrowScope()) {
-        if (!findInnerTransitiveGuaranteedUses(lbi, foundUses)) {
-          result = meet(result, AddressUseKind::PointerEscape);
-        }
+      // FIXME: if we can assume complete lifetimes, then this should be
+      // as simple as:
+      //   for (Operand *use : lbi->getUses()) {
+      //     if (use->endsLocalBorrowScope()) {
+      if (!findInnerTransitiveGuaranteedUses(lbi, foundUses)) {
+        result = meet(result, AddressUseKind::PointerEscape);
       }
       continue;
     }