cargo-update-recipe-crates: Don't fail for partially empty Cargo.lock

cargo-update-recipe-crates: Don't fail for partially empty Cargo.lock

Do not fail if only some Cargo.lock files are empty. Only fail, if there
are absolutely no dependencies found in any Cargo.lock.

This fixes the following error message, which would occur with "bitbake
-c update_crates python3-orjson":

    ERROR: python3-orjson-3.10.17-r0 do_update_crates: Execution of '.../python3-orjson/3.10.17/temp/run.do_update_crates.70693' failed with exit code 1
    ERROR: Logfile of failure stored in: .../python3-orjson/3.10.17/temp/log.do_update_crates.70693
    Log data follows:
    | DEBUG: Executing python function extend_recipe_sysroot
    | NOTE: Direct dependencies are ['.../sources/oe-core/../oe-core/meta/recipes-devtools/quilt/quilt-native_0.69.bb:do_populate_sysroot', 'virtual:native:.../sources/oe-core/../oe-core/meta/recipes-devtools/patch/patch_2.8.bb:do_populate_sysroot', 'virtual:native:.../sources/oe-core/../oe-core/meta/recipes-devtools/python/python3_3.13.9.bb:do_populate_sysroot']
    | NOTE: Installed into sysroot: []
    | NOTE: Skipping as already exists in sysroot: ['gettext-minimal-native', 'cmake-native', 'libtool-native', 'quilt-native', 'texinfo-dummy-native', 'openssl-native', 'expat-native', 'ncurses-native', 'util-linux-libuuid-native', 'zlib-native', 'libedit-native', 'make-native', 'patch-native', 'perl-native', 'python3-native', 'bzip2-native', 'xz-native', 'zstd-native', 'attr-native', 'gdbm-native', 'libffi-native', 'sqlite3-native']
    | DEBUG: Python function extend_recipe_sysroot finished
    | DEBUG: Executing shell function do_update_crates
    | Traceback (most recent call last):
    |   File "<stdin>", line 41, in <module>
    |   File "<stdin>", line 12, in get_crates
    | ValueError: Unable to find any candidate crates that use crates.io
    |
    | The above exception was the direct cause of the following exception:
    |
    | Traceback (most recent call last):
    |   File "<stdin>", line 43, in <module>
    | ValueError: Cannot parse '.../python3-orjson/3.10.17/sources/orjson-3.10.17/include/cargo/simdutf8-0.1.5/Cargo.lock'
    | WARNING: exit code 1 from a shell command.
    ERROR: Task (.../sources/oe-core/../meta-openembedded/meta-python/recipes-devtools/python/python3-orjson_3.10.17.bb:do_update_crates) failed with exit code '1'

Signed-off-by: Martin Schwan <m.schwan@phytec.de>
Signed-off-by: Mathieu Dubois-Briand <mathieu.dubois-briand@bootlin.com>
Signed-off-by: Ross Burton <ross.burton@arm.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>