Fixed Metal.

src/renderer_mtl.mm

@@ -3640,7 +3640,7 @@ namespace bgfx { namespace mtl
 
 				bool programChanged = false;
 				bool constantsChanged = draw.m_uniformBegin < draw.m_uniformEnd;
-				rendererUpdateUniforms(this, _render->m_uniformBuffer, draw.m_uniformBegin, draw.m_uniformEnd);
+				rendererUpdateUniforms(this, _render->m_uniformBuffer[draw.m_uniformIdx], draw.m_uniformBegin, draw.m_uniformEnd);
 
 				if (key.m_program != programIdx
 				|| (BGFX_STATE_BLEND_MASK|BGFX_STATE_BLEND_EQUATION_MASK|BGFX_STATE_ALPHA_WRITE|BGFX_STATE_RGB_WRITE|BGFX_STATE_BLEND_INDEPENDENT|BGFX_STATE_MSAA|BGFX_STATE_BLEND_ALPHA_TO_COVERAGE) & changedFlags