Narrowed Shell Issue

this only occurs when the variables are the result of a command.
Example:

a='hello '
b='world'
c=$a$b
echo $c

This works. Output: hello world

Provider=$(adb shell getprop gsm.operator.alpha)
Model=$(adb shell getprop ro.product.model)
c=$Provider$Model
echo $c

Fails. Output: Nexus 5e