diff --git a/server/lib/classes/file.inc.php b/server/lib/classes/file.inc.php
index 0cfdf6f2eddcb62489b2c7af490679e261b93b65..d3117c36dcad9ce2750a7dd282228319807777f9 100644
--- a/server/lib/classes/file.inc.php
+++ b/server/lib/classes/file.inc.php
@@ -124,9 +124,11 @@ class file{
 				if(trim($line) != '') $new_lines[] = $line;
 			}
 		}
-
-		$content = implode("\n", $new_lines);
-
+		if(!empty($new_lines)){
+			$content = implode("\n", $new_lines);
+		} else {
+			$content = '';
+		}
 		if($file){
 			$this->wf($input, $content);
 		} else {
diff --git a/server/plugins-available/shelluser_base_plugin.inc.php b/server/plugins-available/shelluser_base_plugin.inc.php
index 2fc4f0dfc7cdc0b657825dbdfe51fbb299794b53..cb4684319781820e053864f4029661aa73066a8e 100755
--- a/server/plugins-available/shelluser_base_plugin.inc.php
+++ b/server/plugins-available/shelluser_base_plugin.inc.php
@@ -477,7 +477,11 @@ class shelluser_base_plugin {
 			// Remove duplicate keys
 			$existing_keys = @file($sshkeys, FILE_IGNORE_NEW_LINES);
 			$new_keys = explode("\n", $userkey);
-			$final_keys_arr = @array_merge($existing_keys, $new_keys);
+			if(is_array($existing_keys)) {
+				$final_keys_arr = @array_merge($existing_keys, $new_keys);
+			} else {
+				$final_keys_arr = $new_keys;
+			}
 			$new_final_keys_arr = array();
 			if(is_array($final_keys_arr) && !empty($final_keys_arr)){
 				foreach($final_keys_arr as $key => $val){
diff --git a/server/plugins-available/shelluser_jailkit_plugin.inc.php b/server/plugins-available/shelluser_jailkit_plugin.inc.php
index dbc3d8041b22b72180cf49a9eb9a931f7454796c..1b2ff74db912b89960de3f74274ea5a1b90fbbb6 100755
--- a/server/plugins-available/shelluser_jailkit_plugin.inc.php
+++ b/server/plugins-available/shelluser_jailkit_plugin.inc.php
@@ -318,6 +318,8 @@ class shelluser_jailkit_plugin {
 				$options = array('hardlink');
 			} elseif ($this->jailkit_config['jailkit_hardlinks'] == 'no') {
 				$options = array();
+			} else {
+				$options = array();
 			}
 		} else {
 			$options = array('allow_hardlink');
@@ -527,7 +529,11 @@ class shelluser_jailkit_plugin {
 			// Remove duplicate keys
 			$existing_keys = @file($sshkeys, FILE_IGNORE_NEW_LINES);
 			$new_keys = explode("\n", $userkey);
-			$final_keys_arr = @array_merge($existing_keys, $new_keys);
+			if(is_array($existing_keys)) {
+				$final_keys_arr = @array_merge($existing_keys, $new_keys);
+			} else {
+				$final_keys_arr = $new_keys;
+			}
 			$new_final_keys_arr = array();
 			if(is_array($final_keys_arr) && !empty($final_keys_arr)){
 				foreach($final_keys_arr as $key => $val){