Don't try to strlen() an array

This is definitely an array now.

Auditors: joshuaspence

src/applications/harbormaster/storage/build/HarbormasterBuildUnitMessage.php

@@ -52,7 +52,7 @@ final class HarbormasterBuildUnitMessage
     }
 
     $coverage = idx($dict, 'coverage');
-    if (strlen($coverage)) {
+    if ($coverage) {
       $obj->setProperty('coverage', $coverage);
     }