Fix download size int casting (#244)

Fixed an int casting issue that caused weird download failures, improve
error handling and added missing return statement which unintentionally
forwarded data to the game (without the socket even being there)

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src/Network/GlobalHandler.cpp

@@ -199,6 +199,7 @@ void ParserAsync(std::string_view Data) {
         return;
     case 'U':
         magic = Data.substr(1);
+        return;
     default:
         break;
     }

src/Network/Resources.cpp

@@ -163,7 +163,12 @@ std::vector<char> TCPRcvRaw(SOCKET Sock, uint64_t& GRcv, uint64_t Size) {
     int i = 0;
     do {
         // receive at most some MB at a time
-        int Len = std::min(int(Size - Rcv), 1 * 1024 * 1024);
+        uint64_t Len = std::min<uint64_t>((Size - Rcv), 1 * 1024 * 1024);
+        if (Len == 0) {
+            error("Download size miscalculation");
+            break;
+        }
+
         int Temp = RecvWaitAll(Sock, &File[Rcv], Len);
         if (Temp == -1 || Temp == 0) {
             debug("Recv returned: " + std::to_string(Temp));
@@ -579,7 +584,12 @@ void NewSyncResources(SOCKET Sock, const std::string& Mods, const std::vector<Mo
             }
 #endif
 
-            fs::copy_file(PathToSaveTo, std::filesystem::path(GetGamePath()) / "mods/multiplayer" / FName, fs::copy_options::overwrite_existing);
+            std::error_code ec;
+            fs::copy_file(PathToSaveTo, std::filesystem::path(GetGamePath()) / "mods/multiplayer" / FName, fs::copy_options::overwrite_existing, ec);
+            if (ec) {
+                error(beammp_wide("Error in copy_file during download of ") + beammp_fs_string(PathToSaveTo) + beammp_wide(": ") + Utils::ToWString(ec.message()));
+                break;
+            }
             UpdateModUsage(FName);
         }
         WaitForConfirm();