GCC 9: error: '<anonymous>.ShaderGLES2::Version::frag_id' is used uninitialized in this function [-Werror=uninitialized]

[marxin]

Godot version:

ce352ce

OS/device including version:

Issue description:

I see a compilation warning with GCC 9:

$ scons progress=yes verbose=yes -j1 platform=x11 tools=no   target=release_debug warnings=extra use_lto=0 werror=1
...
[ 65%] g++ -o drivers/gles2/shader_gles2.x11.opt.debug.64.o -c -std=c++11 -Wctor-dtor-privacy -Wnon-virtual-dtor -Wnoexcept -Wplacement-new=1 -g1 -O2 -pipe -fpie -Wall -Wextra -Wno-unused-parameter -Wwrite-strings -Wshadow-local -Walloc-zero -Wduplicated-branches -Wduplicated-cond -Wstringop-overflow=4 -Wlogical-op -Wattribute-alias=2 -Werror -DDEBUG_ENABLED -DTOUCH_ENABLED -DALSA_ENABLED -DALSAMIDI_ENABLED -DPULSEAUDIO_ENABLED -D_REENTRANT -DJOYDEV_ENABLED -DX11_ENABLED -DUNIX_ENABLED -DOPENGL_ENABLED -DGLES_ENABLED -DPTRCALL_ENABLED -DGDSCRIPT_ENABLED -DMINIZIP_ENABLED -DZSTD_STATIC_LINKING_ONLY -DGLAD_ENABLED -DGLES_OVER_GL -DFREETYPE_ENABLED -DSVG_ENABLED -DHAVE_MNTENT -Ithirdparty/nanosvg -Ithirdparty/freetype/include -Ithirdparty/libpng -Ithirdparty/glad -Ithirdparty/zstd -Ithirdparty/zlib -Iplatform/x11 -I. drivers/gles2/shader_gles2.cpp

In file included from drivers/gles2/shader_gles2.cpp:31:
drivers/gles2/shader_gles2.h: In member function 'HashMap<TKey, TData, Hasher, Comparator, MIN_HASH_TABLE_POWER, RELATIONSHIP>::Element* HashMap<TKey, TData, Hasher, Comparator, MIN_HASH_TABLE_POWER, RELATIONSHIP>::create_element(const TKey&) [with TKey = ShaderGLES2::VersionKey; TData = ShaderGLES2::Version; Hasher = ShaderGLES2::VersionKeyHash; Comparator = HashMapComparatorDefault<ShaderGLES2::VersionKey>; unsigned char MIN_HASH_TABLE_POWER = 3; unsigned char RELATIONSHIP = 8]':
drivers/gles2/shader_gles2.h:110:9: error: '<anonymous>.ShaderGLES2::Version::frag_id' is used uninitialized in this function [-Werror=uninitialized]
  110 |  struct Version {
      |         ^~~~~~~
drivers/gles2/shader_gles2.h:110:9: error: '<anonymous>' is used uninitialized in this function [-Werror=uninitialized]
cc1plus: all warnings being treated as errors
scons: *** [drivers/gles2/shader_gles2.x11.opt.debug.64.o] Error 1
scons: building terminated because of errors.

Steps to reproduce:
The issue started with the mentioned revision. One can see it here:
https://travis-ci.org/godotengine/godot/jobs/606026116?utm_medium=notification&utm_source=github_status

Minimal reproduction project: