fix: possible nil deref in admin_info (#3500)

Author: wooffie

api/admin_info.go

@@ -1121,12 +1121,13 @@ LabelsWaitLoop:
 				if inStep != nil && *inStep > 0 {
 					step = *inStep
 				}
-				if step > 0 {
-					extraParamters = fmt.Sprintf("%s&step=%d", extraParamters, step)
-				}
 
 				if inStart != nil && inEnd != nil {
-					extraParamters = fmt.Sprintf("&start=%d&end=%d&step=%d", *inStart, *inEnd, *inStep)
+					extraParamters = fmt.Sprintf("&start=%d&end=%d", *inStart, *inEnd)
+				}
+
+				if step > 0 {
+					extraParamters = fmt.Sprintf("%s&step=%d", extraParamters, step)
 				}
 
 				// replace the `$__rate_interval` global for step with unit (s for seconds)