Clear lastException if it is not the cause. (#2768)

Clear lastException if it is not the cause.

If another retry or timeout exception would be caused by a false or null value, the last exception is not the cause of the timeout.

Author: joshbruning

java/client/src/org/openqa/selenium/support/ui/FluentWait.java

@@ -243,6 +243,11 @@ public <V> V until(Function<? super T, V> isTrue) {
         } else if (value != null) {
           return value;
         }
+
+        // Clear the last exception; if another retry or timeout exception would
+        // be caused by a false or null value, the last exception is not the
+        // cause of the timeout.
+        lastException = null;
       } catch (Throwable e) {
         lastException = propagateIfNotIgnored(e);
       }