handle malformed json

Author: lsmith77

src/GettextPOGenerator.php

@@ -164,7 +164,10 @@ private function addStringsFromJsonFiles($translations) {
 
         // Load each JSON file to get source strings
         foreach ($this->JsonFiles() as $jsonFile) {
-            $jsonTranslations = json_decode(file_get_contents($jsonFile), true);
+        $jsonTranslations = json_decode(file_get_contents($jsonFile), true);
+            if (!is_array($jsonTranslations)) {
+                throw new \Exception("The file '$jsonFile' is not valid JSON.'");
+            }
 
             foreach ($jsonTranslations as $key => $value) {
                 $sourceStrings[] = $key;