Fix editor crash when shader has incorrect global array declaration

[jsjtxietian]

Trying to fix #90683

The crash happens around the change in shader_compiler.cpp, in that condition, cnode->array_declarations[0].initializer has size 0 and thus use i=1 to index it will crash the editor. I leave it as a safe guard there.

Note that const bool array[1] = bool[];; will cause the crash but const bool array[1] = bool[]; won't (just trigger Expected a ',' or ';'), the changes I made in shader_language.cpp prevent this by simply don't allow a global const array to be defined without initialization, I checked the doc it didn't say whether it's legal or not, so it might not be a good idea. Feel free to correct me.