GL: one more iteration on the Apple buffer texture workaround.

This broke DSA-less contexts with ARB_multi_bind present.

src/Magnum/GL/AbstractTexture.cpp

@@ -539,9 +539,12 @@ void AbstractTexture::bindInternal() {
 
     /* Update state tracker, bind the texture to the unit. Not directly calling
        glBindTexture() here because we may need to include various
-       platform-specific workarounds (Apple, Intel Windpws) */
+       platform-specific workarounds (Apple, Intel Windpws), also can't just
+       reuse textureState.bindImplementation as we *need* to call
+       glBindTexture() in order to create it and have ObjectFlag::Created set
+       (which is then asserted in createIfNotAlready()) */
     textureState.bindings[internalTextureUnit] = {_target, _id};
-    (this->*textureState.bindImplementation)(internalTextureUnit);
+    (this->*textureState.bindInternalImplementation)(internalTextureUnit);
 }
 
 #if !defined(MAGNUM_TARGET_GLES) || defined(MAGNUM_TARGET_GLES2)

src/Magnum/GL/Implementation/TextureState.cpp

@@ -103,6 +103,8 @@ TextureState::TextureState(Context& context, std::vector<std::string>& extension
     #endif
     {
         unbindImplementation = &AbstractTexture::unbindImplementationDefault;
+        /* This is additionally modified below for the
+           apple-buffer-texture-unbind-on-buffer-modify workaround */
         bindImplementation = &AbstractTexture::bindImplementationDefault;
     }
 
@@ -495,8 +497,13 @@ TextureState::TextureState(Context& context, std::vector<std::string>& extension
            implement the workaround also for bindMultiImplementation */
         CORRADE_INTERNAL_ASSERT(!context.isExtensionSupported<Extensions::ARB::multi_bind>());
         bindImplementation = &AbstractTexture::bindImplementationAppleBufferTextureWorkaround;
-    }
+        bindInternalImplementation = &AbstractTexture::bindImplementationAppleBufferTextureWorkaround;
+    } else
     #endif
+    {
+        /* bindImplementation already set above */
+        bindInternalImplementation = &AbstractTexture::bindImplementationDefault;
+    }
 
     #if !defined(MAGNUM_TARGET_GLES2) && !defined(MAGNUM_TARGET_WEBGL)
     /* Allocate image bindings array to hold all possible image units */

src/Magnum/GL/Implementation/TextureState.h

@@ -63,6 +63,7 @@ struct TextureState {
     void(*bindMultiImplementation)(GLint, Containers::ArrayView<AbstractTexture* const>);
     void(AbstractTexture::*createImplementation)();
     void(AbstractTexture::*bindImplementation)(GLint);
+    void(AbstractTexture::*bindInternalImplementation)(GLint);
     void(AbstractTexture::*parameteriImplementation)(GLenum, GLint);
     void(AbstractTexture::*parameterfImplementation)(GLenum, GLfloat);
     #ifndef MAGNUM_TARGET_GLES2