fixes

src/logic/scripting/lua/libs/libapp.cpp

@@ -4,12 +4,16 @@
 #include "io/devices/MemoryDevice.hpp"
 
 static int l_create_memory_device(lua::State* L) {
-    auto name = lua::require_string(L, 1);
+    std::string name = lua::require_string(L, 1);
     if (io::get_device(name)) {
         throw std::runtime_error(
-            "entry-point '" + std::string(name) + "' is already used"
+            "entry-point '" + name + "' is already used"
         );
     }
+    if (name.find(':') != std::string::npos) {
+        throw std::runtime_error("invalid entry point name");
+    }
+    
     io::set_device(name, std::make_unique<io::MemoryDevice>());
     return 0;
 }

src/logic/scripting/lua/libs/libfile.cpp

@@ -5,6 +5,7 @@
 #include "engine/Engine.hpp"
 #include "engine/EnginePaths.hpp"
 #include "io/io.hpp"
+#include "io/devices/MemoryDevice.hpp"
 #include "io/devices/ZipFileDevice.hpp"
 #include "util/stringutil.hpp"
 #include "api_lua.hpp"
@@ -49,6 +50,14 @@ static bool is_writeable(const std::string& entryPoint) {
     if (entryPoint.substr(0, 2) == "W.") {
         return true;
     }
+    // todo: do better
+    auto device = io::get_device(entryPoint);
+    if (device == nullptr) {
+        return false;
+    }
+    if (dynamic_cast<io::MemoryDevice*>(device.get())) {
+        return true;
+    }
     if (writeable_entry_points.find(entryPoint) != writeable_entry_points.end()) {
         return true;
     }