Avoid negative _claims

src/helpers/RefCountedDigitalPin.h

@@ -22,10 +22,11 @@ public:
   }
 
   void release() {
+    if (_claims == 0) return; // avoid negative _claims
+
+    _claims--;
     if (_claims == 0) {
       digitalWrite(_pin, !_active);
-    } else {
-      _claims--;
     }
   }
 };