fix: Fix a crash in firefox_addons

Add a return When the "addons" member in the extensions JSON
is present but it's not an array,
to avoid accessing uninitialized memory.

osquery/tables/applications/browser_firefox.cpp

@@ -17,7 +17,6 @@
 #include <osquery/utils/conversions/tryto.h>
 
 namespace fs = boost::filesystem;
-namespace pt = boost::property_tree;
 
 namespace osquery {
 
@@ -120,6 +119,7 @@ void genFirefoxAddonsFromExtensions(const std::string& uid,
     TLOG << "Unrecognized format for the 'addons' member in the extensions "
             "file at: "
          << extensions_path << ", it's not an array";
+    return;
   }
 
   for (const auto& addon : addons.GetArray()) {