DBG: Fixing invalid free (x64dbg#438)

Author: Nukem9

src/dbg/memory.cpp

@@ -183,7 +183,9 @@ void MemUpdateMap()
         }
     }
 
-    BridgeFree(threadList.list);
+    // Only free thread data if it was allocated
+    if (threadList.list)
+        BridgeFree(threadList.list);
 
     // Convert the vector to a map
     EXCLUSIVE_ACQUIRE(LockMemoryPages);

src/dbg/thread.cpp

@@ -76,6 +76,7 @@ void ThreadGetList(THREADLIST* List)
     // Also assume BridgeAlloc zeros the returned buffer.
     //
     List->count = (int)threadList.size();
+    List->list = nullptr;
 
     if (List->count <= 0)
         return;