fix typo that broke all the builds

Bug: 7584338
Change-Id: Ieb8c27a544ac583af9aa1e0376e33a673d2d9673
diff --git a/libs/gui/BufferQueue.cpp b/libs/gui/BufferQueue.cpp
index 607e0bd..086e298 100644
--- a/libs/gui/BufferQueue.cpp
+++ b/libs/gui/BufferQueue.cpp
@@ -314,12 +314,9 @@
                      * the consumer may still have pending reads of the
                      * buffers in flight.
                      */
-                    if (found >= 0) {
-                        bool isOlder = mSlots[i].mFrameNumber <
-                                mSlots[found].mFrameNumber;
-                        if (isOlder) {
-                            found = i;
-                        }
+                    if ((found < 0) ||
+                            mSlots[i].mFrameNumber < mSlots[found].mFrameNumber) {
+                        found = i;
                     }
                 }
             }