Compile error for Px4, remind "IndexError: list index out of range"

When I execute the “make px4fmu-v2_default” command to make px4 v1.6.2 code, It remind me this error.
Who has seen this problem?

– Nuttx build for px4fmu-v2 on m4 hardware, using nsh with ROMFS on px4fmu_common
– Build Type: MinSizeRel
Traceback (most recent call last):
File “Tools/tag_to_version.py”, line 19, in
minor = res[1]
IndexError: list index out of range
– PX4 VERSION: 3284b7d
– CONFIG: nuttx-px4fmu-v2-default
– The ASM compiler identification is GNU
– Found assembler: /home/yst/gcc-arm-none-eabi-7-2017-q4-major/bin/arm-none-eabi-gcc
– Found PythonInterp: /usr/bin/python (found version “2.7.12”)
– Found PY_jinja2: /usr/local/lib/python2.7/dist-packages/jinja2
– C compiler: arm-none-eabi-gcc (GNU Tools for Arm Embedded Processors 7-2017-q4-major) 7.2.1 20170904 (release) [ARM/embedded-7-branch revision 255204]
– C++ compiler: arm-none-eabi-g++ (GNU Tools for Arm Embedded Processors 7-2017-q4-major) 7.2.1 20170904 (release) [ARM/embedded-7-branch revision 255204]
– Adding ROMFS on px4fmu-v2
– Nuttx build for px4fmu-v2 on m3 hardware, using nsh
– Configuring done
– Generating done
– Build files have been written to: /home/yst/px4_code/px4_0/xyi_px4/build_px4fmu-v2_default
[73/566] Building NuttX for px4io-v2 with nsh
FAILED: cd /home/yst/px4_code/px4_0/xyi_px4/build_px4fmu-v2_default/px4io-v2 && /bin/rm -rf /home/yst/px4_code/px4_0/xyi_px4/build_px4fmu-v2_default/px4io-v2/NuttX/nuttx/nuttx-export && /usr/bin/make --quiet --no-print-directory -C /home/yst/px4_code/px4_0/xyi_px4/build_px4fmu-v2_default/px4io-v2/NuttX/nuttx -r CONFIG_ARCH_BOARD=px4io-v2 export >nuttx_build.log && cmake -E touch /home/yst/px4_code/px4_0/xyi_px4/build_px4fmu-v2_default/px4io-v2/nuttx_export.stamp
stdio/lib_sscanf.c: In function ‘vsscanf’:
stdio/lib_sscanf.c:419:28: error: this statement may fall through [-Werror=implicit-fallthrough=]
sign = true;
^
stdio/lib_sscanf.c:420:21: note: here
case ‘u’:
^~~~
cc1: all warnings being treated as errors
make[2]: *** [bin/lib_sscanf.o] Error 1
make[1]: *** [libc/libc.a] Error 2
[73/566] Building NuttX for px4fmu-v2 with nsh
FAILED: cd /home/yst/px4_code/px4_0/xyi_px4/build_px4fmu-v2_default/px4fmu-v2 && /bin/rm -rf /home/yst/px4_code/px4_0/xyi_px4/build_px4fmu-v2_default/px4fmu-v2/NuttX/nuttx/nuttx-export && /usr/bin/make --quiet --no-print-directory -C /home/yst/px4_code/px4_0/xyi_px4/build_px4fmu-v2_default/px4fmu-v2/NuttX/nuttx -r CONFIG_ARCH_BOARD=px4fmu-v2 export >nuttx_build.log && cmake -E touch /home/yst/px4_code/px4_0/xyi_px4/build_px4fmu-v2_default/px4fmu-v2/nuttx_export.stamp
stdio/lib_sscanf.c: In function ‘vsscanf’:
stdio/lib_sscanf.c:419:28: error: this statement may fall through [-Werror=implicit-fallthrough=]
sign = true;
^
stdio/lib_sscanf.c:420:21: note: here
case ‘u’:
^~~~
cc1: all warnings being treated as errors
make[2]: *** [bin/lib_sscanf.o] Error 1
make[1]: *** [libc/libc.a] Error 2
ninja: build stopped: subcommand failed.
Makefile:164: recipe for target ‘px4fmu-v2_default’ failed
make: *** [px4fmu-v2_default] Error 1

This error basically means you are trying to access a value at a List index which is out of bounds i.e greater than the last index of the list or less than the least index in the list. So the first element is 0, second is 1, so on. So if there are n elements in a python list, the last element is n-1 . If you try to access the empty or None element by pointing available index of the list, then you will get the "List index out of range " error. To solve this error, you should make sure that you’re not trying to access a non-existent item in a list.