Fix bug caused by using LogWarningFormat instead of LogWarning

Put output id uniform first in MaterialPropertyBlock, so that it's hit early when setting it for every node

MaterialGraphProject/Assets/UnityShaderEditor/Editor/Drawing/PreviewManager.cs

 
             // Fill MaterialPropertyBlock
             m_PreviewPropertyBlock.Clear();
+            var outputIdName = m_OutputIdProperty != null ? m_OutputIdProperty.referenceName : null;
+            m_PreviewPropertyBlock.SetFloat(outputIdName, -1);
             foreach (var nodeGuid in m_PropertyNodeGuids)
             {
                 var node = m_Graph.GetNodeFromGuid<AbstractMaterialNode>(nodeGuid);
                 m_PreviewProperties.Clear();
             }
 
-            var outputIdName = m_OutputIdProperty != null ? m_OutputIdProperty.referenceName : null;
 
             foreach (var nodeGuid in m_DirtyPreviews)
             {
             // Debug output
             var message = "RecreateShader: " + node.GetVariableNameForNode() + Environment.NewLine + previewData.shaderString;
             if (MaterialGraphAsset.ShaderHasError(previewData.shader))
-                Debug.LogWarningFormat(message);
+                Debug.LogWarning(message);
             else
                 Debug.Log(message);
         }