Fix typo in comment

Thanks to @timgates42 for pointing this out.
diff --git a/src/libusbmuxd.c b/src/libusbmuxd.c
index b16936a..23d549b 100644
--- a/src/libusbmuxd.c
+++ b/src/libusbmuxd.c
@@ -1380,7 +1380,7 @@
 			free(payload);
 		} else {
 			// we _should_ have all of them now.
-			// or perhaps an error occured.
+			// or perhaps an error occurred.
 			break;
 		}
 	}