ModuleManager: Simplify lookupModuleFile by only setting the out parameter once, NFC

[JDevlieghere]

LGTM

clang/lib/Serialization/ModuleManager.cpp

void ModuleManager::visit(llvm::function_ref<bool(ModuleFile &M)> Visitor,
 
   returnVisitState(State);
 }
 
 bool ModuleManager::lookupModuleFile(StringRef FileName,
                                      off_t ExpectedSize,
                                      time_t ExpectedModTime,
                                      const FileEntry *&File) {
-  if (FileName == "-") {
-    File = nullptr;
+  if (FileName == "-")
     return false;
-  }
 
   // Open the file immediately to ensure there is no race between stat'ing and
   // opening the file.
   auto FileOrErr = FileMgr.getFile(FileName, /*OpenFile=*/true,
                                    /*CacheFailure=*/false);
-  if (!FileOrErr) {
-    File = nullptr;
+  if (!FileOrErr)
     return false;
-  }
+
   File = *FileOrErr;
 
   if ((ExpectedSize && ExpectedSize != File->getSize()) ||
       (ExpectedModTime && ExpectedModTime != File->getModificationTime()))
     // Do not destroy File, as it may be referenced. If we need to rebuild it,
     // it will be destroyed by removeModules.
     return true;