Add bugprone-optional-value-conversion

And fix the one case.

Change-Id: Iaaedf56b12cae38583ae82017ebea8bfe8987689
Signed-off-by: Ed Tanous <ed@tanous.net>
diff --git a/.clang-tidy b/.clang-tidy
index fb31ead..46561c1 100644
--- a/.clang-tidy
+++ b/.clang-tidy
@@ -26,6 +26,7 @@
 bugprone-misplaced-widening-cast,
 bugprone-move-forwarding-reference,
 bugprone-multiple-statement-macro,
+bugprone-optional-value-conversion,
 bugprone-no-escape,
 bugprone-not-null-terminated-result,
 bugprone-parent-virtual-call,