MissingComponentException Warning

 IEnumerator ChildDissolve(float endValue, float duration)
     {
         float time = 0;
         float startValue = _ChildDissolveValue;
         while (time < duration)
         {
             int children = transform.childCount; // Getting Child material from MeshRenderer.
             for (int i = 0; i < children; i++)
             {
                 GameObject _CurrentChild = transform.GetChild(i).gameObject;
                 for (int j = 0; j < children; j++)
                 {
                     //if (_CurrentChild.GetComponent<MeshRenderer>() != null) // some child materials do not use a mesh renderer component.
                     {
                         // Code A doesnt work inside this check! (Creates extreme performance issues)
                         //Material _ChildMaterial = _CurrentChild.GetComponent<MeshRenderer>().material;
                         //float _ChildDissolveValue = _ChildMaterial.GetFloat("Dissolve"); // Variable I need.
                     }
                     
                     // Code A: only working outside of statement. (122-123)
                     Material _ChildMaterial = _CurrentChild.GetComponent<MeshRenderer>().material;
                     float _ChildDissolveValue = _ChildMaterial.GetFloat("Dissolve"); // Variable I need.
                     
                     _ChildMaterial.SetFloat("Dissolve", (Mathf.Lerp(startValue, endValue, time / duration)));
                 }
             }
             time += Time.deltaTime;
             yield return null;
         }
         _ChildMaterial.SetFloat("Dissolve", endValue);
     }

The line:

 _ChildMaterial.SetFloat("Dissolve", (Mathf.Lerp(startValue, endValue, time / duration)));

This is giving me errors I've tried to write a null component exception if the current child is missing a MeshRenderer component and stick the code inside it. But not only does it break game functionality, the performance is not acceptable!

How could one check to see if a MeshRenderer has the "Dissolve" float? The code works as is, I just can't seem to resolve this console warning.