master branch might not exist

After a fresh install I was unable to run the installer again. It was breaking with the error

error: branch 'master' not found.

my fix makes sure that the installer continues after that.

install.sh

@@ -44,7 +44,7 @@ install_nvm_from_git() {
     mkdir -p "$NVM_DIR"
     git clone "$NVM_SOURCE" "$NVM_DIR"
   fi
-  cd $NVM_DIR && git checkout v0.11.2 && git branch -D master
+  cd $NVM_DIR && git checkout v0.11.2 && git branch -D master || true
 }
 
 install_nvm_as_script() {