Resolve clang-tidy error:

rwgk · rwgk · commit df27188dc6d6 · 2023-11-07T09:19:24.000-08:00
```
include/pybind11/detail/type_caster_base.h:795:21: error: the 'empty' method should be used to check for emptiness instead of 'size' [readability-container-size-empty,-warnings-as-errors]
                if (matching_bases.size() != 0) {
                    ^~~~~~~~~~~~~~~~~~~~~~~~~~
                    !matching_bases.empty()
```
diff --git a/include/pybind11/detail/type_caster_base.h b/include/pybind11/detail/type_caster_base.h
@@ -792,7 +792,7 @@ class type_caster_generic {
                         matching_bases.push_back(base);
                     }
                 }
-                if (matching_bases.size() != 0) {
+                if (!matching_bases.empty()) {
                     if (matching_bases.size() > 1) {
                         matching_bases.push_back(const_cast<type_info *>(typeinfo));
                         all_type_info_check_for_divergence(matching_bases);

Original file line number	Diff line number	Diff line change
`@@ -792,7 +792,7 @@ class type_caster_generic {`
`792`	`792`	`matching_bases.push_back(base);`
`793`	`793`	`}`
`794`	`794`	`}`
`795`		`- if (matching_bases.size() != 0) {`
	`795`	`+ if (!matching_bases.empty()) {`
`796`	`796`	`if (matching_bases.size() > 1) {`
`797`	`797`	`matching_bases.push_back(const_cast<type_info *>(typeinfo));`
`798`	`798`	`all_type_info_check_for_divergence(matching_bases);`