Fix SQL injection vulnerability in orderby parameter across all helper files

Co-authored-by: iftakharul-islam <88052038+iftakharul-islam@users.noreply.github.com>

Author: Copilot

src/Activity/Helper/Activity.php

@@ -598,7 +598,9 @@ private function orderby() {
 			$order[] =  $this->tb_activity . '.' . esc_sql($key) . ' ' . esc_sql($value);
         }
 
-        $this->orderby = "ORDER BY " . implode( ', ', $order);
+        if ( !empty( $order ) ) {
+            $this->orderby = "ORDER BY " . implode( ', ', $order );
+        }
 
         return $this;
     }

src/Comment/Helper/Comment.php

@@ -395,7 +395,9 @@ private function orderby() {
 			$order[] =  $tb_pj . '.' . esc_sql($key) . ' ' . esc_sql($value);
         }
 
-        $this->orderby = "ORDER BY " . implode( ', ', $order);
+        if ( !empty( $order ) ) {
+            $this->orderby = "ORDER BY " . implode( ', ', $order );
+        }
 
         return $this;
     }

src/Discussion_Board/Helper/Discussion_Board.php

@@ -690,7 +690,9 @@ private function orderby() {
 			$order[] =  $tb_pj . '.' . esc_sql($key) . ' ' . esc_sql($value);
         }
 
-        $this->orderby = "ORDER BY " . implode( ', ', $order);
+        if ( !empty( $order ) ) {
+            $this->orderby = "ORDER BY " . implode( ', ', $order );
+        }
 
         return $this;
     }

src/File/Helper/File.php

@@ -328,7 +328,9 @@ private function orderby() {
 			$order[] =  $tb_pj . '.' . esc_sql($key) . ' ' . esc_sql($value);
         }
 
-        $this->orderby = "ORDER BY " . implode( ', ', $order);
+        if ( !empty( $order ) ) {
+            $this->orderby = "ORDER BY " . implode( ', ', $order );
+        }
 
         return $this;
     }

src/Milestone/Helper/Milestone.php

@@ -597,7 +597,9 @@ private function orderby() {
 			$order[] =  $tb_pj . '.' . esc_sql($key) . ' ' . esc_sql($value);
         }
 
-        $this->orderby = "ORDER BY " . implode( ', ', $order);
+        if ( !empty( $order ) ) {
+            $this->orderby = "ORDER BY " . implode( ', ', $order );
+        }
 
         return $this;
     }

src/Task/Helper/Task.php

@@ -1950,7 +1950,9 @@ private function orderby() {
 			$order[] =  $tb_pj . '.' . esc_sql($key) . ' ' . esc_sql($value);
 	    }
 
-	    $this->orderby = "ORDER BY " . implode( ', ', $order);
+	    if ( !empty( $order ) ) {
+	        $this->orderby = "ORDER BY " . implode( ', ', $order );
+	    }
 
 		return $this;
 	}

src/Task_List/Helper/Task_List.php

@@ -1002,7 +1002,9 @@ private function orderby() {
 			$order[] =  $tb_pj . '.' . esc_sql($key) . ' ' . esc_sql($value);
         }
 
-        $this->orderby = "ORDER BY " . implode( ', ', $order);
+        if ( !empty( $order ) ) {
+            $this->orderby = "ORDER BY " . implode( ', ', $order );
+        }
 
         return $this;
     }

src/User/Helper/User.php

@@ -221,7 +221,9 @@ private function orderby() {
 			$order[] =  $tb_pj . '.' . esc_sql($key) . ' ' . esc_sql($value);
         }
 
-        $this->orderby = "ORDER BY " . implode( ', ', $order);
+        if ( !empty( $order ) ) {
+            $this->orderby = "ORDER BY " . implode( ', ', $order );
+        }
 
         return $this;
     }