Attempt to invoke virtual method 'java.lang.String LowerCase()'on a null object reference

Hello Friends,I am having this problem in my app. I google it and also search in the community but i cannot find suitable solution please help me to solve it. Whenever the chat screen initialize this message is showing and whenever i typing message in the text box , this message is showing.
And also the contact number only showing not the name which is saved.

My blocks
Chat Screen

Home Screen