CStringTable: Make unrecognized image type a warning

This can be hit while creating a project. However this would be hit in
release mode too, but wouldn't crash the application, because the trap
signal is ifdef'd out.

src/Core/Resource/StringTable/CStringTable.cpp

@@ -327,7 +327,7 @@ std::unique_ptr<CDependencyTree> CStringTable::BuildDependencyTree() const
                     }
                     else
                     {
-                        errorf("Unrecognized image type: %s", *ImageType);
+                        warnf("Unrecognized image type: %s", *ImageType);
                         continue;
                     }