feat: add null checks for ejsData and function parameters

Author: osm-Jatin

OsmoDoc/Pdf/PdfDocumentGenerator.cs

@@ -24,6 +24,21 @@ public async static Task GeneratePdf(string templatePath, List<ContentMetaData>
     {
         try
         {
+            if (metaDataList is null)
+            {
+                throw new ArgumentNullException(nameof(metaDataList));
+            }
+            
+            if (string.IsNullOrWhiteSpace(templatePath))
+            {
+                throw new ArgumentNullException(nameof(templatePath));
+            }
+
+            if (string.IsNullOrWhiteSpace(outputFilePath))
+            {
+                throw new ArgumentNullException(nameof(outputFilePath));
+            }
+
             if (string.IsNullOrWhiteSpace(OsmoDocPdfConfig.WkhtmltopdfPath) && !RuntimeInformation.IsOSPlatform(OSPlatform.Linux))
             {
                 throw new Exception("WkhtmltopdfPath is not set in OsmoDocPdfConfig.");
@@ -180,7 +195,8 @@ private async static Task<string> ConvertEjsToHTML(string ejsFilePath, string ou
 
         // Write json data string to json file
         string ejsDataJsonFilePath = Path.Combine(tempDirectoryFilePath, "ejsData.json");
-        File.WriteAllText(ejsDataJsonFilePath, ejsDataJson);
+        string contentToWrite = ejsDataJson ?? "{}";
+        File.WriteAllText(ejsDataJsonFilePath, contentToWrite);
 
         string commandLine = "cmd.exe";
         if (RuntimeInformation.IsOSPlatform(OSPlatform.Linux))