Add error handling when not a number as sugested

subjects/sumthemall/README.md

@@ -2,7 +2,7 @@
 
 ### Instructions
 
-Create a program that receives a number of arguments representing whole numbers and displays the sum of the total. If there are not enough arguments or there is an overflow display 0 followed by a new line.
+Create a program that receives a number of arguments representing whole numbers and displays the sum of the total. If there are not enough arguments or there is an overflow display 0 followed by a new line. If the argument is not a number display 0.
 
 ### Usage
 
@@ -11,4 +11,6 @@ $ go run . 23 34 53 | cat -e
 110$
 $ go run . 1000 2000 3000 4000 | cat -e
 10000$
+$ go run . a | cat -e
+0$
 ```