Profiler: Use NonnullOwnPtr for libraries

Userland/DevTools/Profiler/Process.cpp

@@ -109,8 +109,6 @@ String LibraryMetadata::Library::symbolicate(FlatPtr ptr, u32* offset) const
 const LibraryMetadata::Library* LibraryMetadata::library_containing(FlatPtr ptr) const
 {
     for (auto& it : m_libraries) {
-        if (!it.value)
-            continue;
         auto& library = *it.value;
         if (ptr >= library.base && ptr < (library.base + library.size))
             return &library;

Userland/DevTools/Profiler/Process.h

@@ -35,7 +35,7 @@ public:
     const Library* library_containing(FlatPtr) const;
 
 private:
-    mutable HashMap<String, OwnPtr<Library>> m_libraries;
+    mutable HashMap<String, NonnullOwnPtr<Library>> m_libraries;
 };
 
 struct Thread {