Fix file type extension check

uc-people.php

@@ -121,7 +121,8 @@ function importFile( $filename ){
 		    require_once( ABSPATH . 'wp-admin/includes/file.php' );
 		}
 
-		if( $_FILES[$filename]['type'] !== 'text/csv' ){
+		$filePathInfo = pathinfo( $_FILES[$filename]['name'] );
+		if( $filePathInfo['extension'] !== 'csv' ){
 			echo '<div class="error notice is-dismissible below-h2" id="message"><p>Please upload a CSV file</p><button class="notice-dismiss" type="button"><span class="screen-reader-text">Dismiss this notice.</span></button></div>';
 			return;
 		}