Ignore AWS_UNSET_PROFILE in [profile:...]

src/StackFormation/ValueResolver/Stage/ProfileSwitcher.php

@@ -10,14 +10,25 @@ public function invoke($string)
         $string = preg_replace_callback(
             '/\[profile:([^:\]\[]+?):([^\]\[]+?)\]/',
             function ($matches) {
+
+                // [profile:...] ignores AWS_UNSET_PROFILE. Backup up value here
+                $unsetProfileBackup = getenv('AWS_UNSET_PROFILE');
+                putenv('AWS_UNSET_PROFILE');
+
                 // recursively create another ValueResolver, but this time with a different profile
                 $subValueResolver = new \StackFormation\ValueResolver\ValueResolver(
                     $this->valueResolver->getDependencyTracker(),
                     $this->valueResolver->getProfileManager(),
                     $this->valueResolver->getConfig(),
                     $matches[1]
                 );
-                return $subValueResolver->resolvePlaceholders($matches[2], $this->sourceBlueprint, $this->sourceType, $this->sourceKey);
+                $value = $subValueResolver->resolvePlaceholders($matches[2], $this->sourceBlueprint, $this->sourceType, $this->sourceKey);
+
+                // restoring AWS_UNSET_PROFILE value if it was set before
+                if ($unsetProfileBackup) {
+                    putenv('AWS_UNSET_PROFILE=1');
+                }
+                return $value;
             },
             $string
         );