Fix building on GLES2/WebGL.

src/Magnum/AbstractTexture.cpp

@@ -240,11 +240,13 @@ AbstractTexture::~AbstractTexture() {
         if(binding.second == _id) binding = {};
     }
 
+    #if !defined(MAGNUM_TARGET_GLES2) && !defined(MAGNUM_TARGET_WEBGL)
     /* Remove all image bindings */
     for(auto& binding: Context::current().state().texture->imageBindings) {
         /* MSVC 2015 needs the parentheses around */
         if(std::get<0>(binding) == _id) binding = {};
     }
+    #endif
 
     glDeleteTextures(1, &_id);
 }