Update StartHost.cs (#1735)

Fixing issue #1732 
Updating the else if block to skip attempting to set the environmental variable when both the var and it's value are blank or null.

Co-authored-by: Ahmed ElSayed <[email protected]>

Author: TroyWitthoeft

src/Azure.Functions.Cli/Actions/HostActions/StartHostAction.cs

@@ -218,7 +218,7 @@ private void UpdateEnvironmentVariables(IDictionary<string, string> secrets)
                 {
                     Environment.SetEnvironmentVariable(secret.Key, secret.Value, EnvironmentVariableTarget.Process);
                 }
-                else if (secret.Value == string.Empty)
+                else if (!string.IsNullOrEmpty(secret.Key) && secret.Value == string.Empty)
                 {
                     EnvironmentNativeMethods.SetEnvironmentVariable(secret.Key, secret.Value);
                 }