Fix out-of-bounds memory write in KeyAddrEventQueue

This change prevents `KeyAddrEventQueue::remove()` from shifting values in
memory out of bounds of its arrays if `shift()` is called on an empty queue.  It
also adds a check to be sure that the entry removed is in the queue.

Signed-off-by: Michael Richters <gedankenexperimenter@gmail.com>

src/kaleidoscope/KeyAddrEventQueue.h

@@ -103,6 +103,8 @@ class KeyAddrEventQueue {
   // rather than using a ring buffer because we expect it will be called much
   // less often than the queue is searched via a for loop.
   void remove(uint8_t n = 0) {
+    if (n >= length_ || length_ == 0)
+      return;
     // assert(length > n);
     --length_;
     for (uint8_t i{n}; i < length_; ++i) {