Leave unused exception variables unnamed

Thirteen catch clauses named the exception without using it. gcc and
clang accept that silently, but MSVC reports each one as C4101. Drop
the name; the handlers are unchanged.

python/src/file.hpp

@@ -144,7 +144,7 @@ void define_file_io_bindings(py::module &m) {
                 self.read_into(
                     reinterpret_cast<std::byte *>(image.mutable_data()));
                 return image;
-            } catch (std::runtime_error &e) {
+            } catch (std::runtime_error &) {
                 throw py::stop_iteration();
             }
         });

python/src/jungfrau_data_file.hpp

@@ -101,7 +101,7 @@ void define_jungfrau_data_file_io_bindings(py::module &m) {
         .def("__next__", [](JungfrauDataFile &self) {
             try {
                 return read_dat_frame(self);
-            } catch (std::runtime_error &e) {
+            } catch (std::runtime_error &) {
                 throw py::stop_iteration();
             }
         });

python/src/raw_sub_file.hpp

@@ -94,7 +94,7 @@ void define_raw_sub_file_io_bindings(py::module &m) {
         .def("__next__", [](RawSubFile &self) {
             try {
                 return read_frame_from_RawSubFile(self);
-            } catch (std::runtime_error &e) {
+            } catch (std::runtime_error &) {
                 throw py::stop_iteration();
             }
         });