fix: check result when determining exit code of ls <filter>

PR-URL: #1986
Credit: @G-Rath
Close: #1986
Reviewed-by: @ruyadorno

Author: G-Rath

lib/ls.js

@@ -488,7 +488,7 @@ const ls = async (args) => {
   )
 
   // if filtering items, should exit with error code on no results
-  if (!tree[_include] && args.length) {
+  if (result && !result[_include] && args.length) {
     process.exitCode = 1
   }
 

test/lib/ls.js

@@ -2476,6 +2476,11 @@ t.test('ls --json', (t) => {
         },
         'should output json contaning only occurences of filtered by package'
       )
+      t.equal(
+        process.exitCode,
+        0,
+        'should exit with error code 0'
+      )
       t.end()
     })
   })