Skip instances where $file is an empty string

eng/common/TestResources/build-test-resource-config.yml

@@ -66,14 +66,16 @@ steps:
 
       if ($subConfigFilesRaw) {
         $subConfigFiles = $subConfigFilesRaw | ConvertFrom-Json -AsHashtable
-        # Handle cases where $subConfigFilesRaw converts to an empty string
-        # instead of an array of strings
-        if ($subConfigFiles) {
-          foreach ($file in $subConfigFiles) {
-            Write-Host "Merging sub config from file: $file"
-            $subConfig = Get-Content $file | ConvertFrom-Json -AsHashtable
-            $finalConfig = UpdateSubscriptionConfiguration $finalConfig $subConfig
+        foreach ($file in $subConfigFiles) {
+          # In some cases, $file could be an empty string. Get-Content will fail
+          # if $file is an empty string, so skip those cases.
+          if (!$file) {
+            continue
           }
+
+          Write-Host "Merging sub config from file: $file"
+          $subConfig = Get-Content $file | ConvertFrom-Json -AsHashtable
+          $finalConfig = UpdateSubscriptionConfiguration $finalConfig $subConfig
         }
       }