[Fix] (MG_State, MG_Impl/GLImpl): allocating a mipmap level no longer truncates the chain above it - AllocateLevel now only grows and the callers that genuinely redefine the whole level set (glTexStorage*, mip regeneration, multisample storage, level-0 respecification) drop the tail explicitly

MobileGL/MG_State/GLState/TextureState/TextureObject2DCube.cpp

@@ -31,6 +31,10 @@ namespace MobileGL {
                 m_textureStorage.AllocateLevel(GetIndexOfTextureUploadTarget(uploadTarget), mipmapLevel, input);
             }
 
+            void TextureObject2DCube::TruncateMipmapLevels(TextureUploadTarget uploadTarget, Uint levelCount) {
+                m_textureStorage.TruncateToLevelCount(GetIndexOfTextureUploadTarget(uploadTarget), levelCount);
+            }
+
             void TextureObject2DCube::UpdateMipmapSubData(TextureUploadTarget uploadTarget, Uint mipmapLevel,
                                                           DataPtr input) {
                 m_textureStorage.UpdateSubData(GetIndexOfTextureUploadTarget(uploadTarget), mipmapLevel, input);