Added Error Message When File Fails to Write (prasathmani#399)

Added error checking and message for when file fails to write on the server side.  Before this change if a write failed on the server side it would still present the user with a misleading "Saved Successfully" Message.

tinyfilemanager.php

@@ -435,7 +435,12 @@ function session_error_handling_function($code, $msg, $file, $line) {
         $writedata = $_POST['content'];
         $fd = fopen($file_path, "w");
         @fwrite($fd, $writedata);
+        $write_results = @fwrite($fd, $writedata);
         fclose($fd);
+        if ($write_results === false){ 
+            header("HTTP/1.1 500 Internal Server Error");
+            die("Could Not Write File! - Check Permissions / Ownership");
+        }
         die(true);
     }
 
@@ -3743,7 +3748,8 @@ function edit_save(e, t) {
                     contentType: "multipart/form-data-encoded; charset=utf-8",
                     //dataType: "json",
                     success: function(mes){toast("Saved Successfully"); window.onbeforeunload = function() {return}},
-                    failure: function(mes) {toast("Error: try again");}
+                    failure: function(mes) {toast("Error: try again");},
+                    error: function(mes) {toast(`<p style="background-color:red">${mes.responseText}</p>`);}
                 });
 
             }