GDScript: Fix validate_call_arg() for unresolved datatype

[dalexeev]

Fix wrong implication.

#0  GDScriptAnalyzer::is_type_compatible (this=0x7fffffffca30, p_target=..., 
    p_source=..., p_allow_implicit_conversion=true, p_source_node=0x0)
    at modules/gdscript/gdscript_analyzer.cpp:4969
#1  0x0000555558c7f359 in GDScriptAnalyzer::validate_call_arg (
    this=0x7fffffffca30, p_par_types=..., p_default_args_count=0, 
    p_is_vararg=false, p_call=0x55557dddd570)
    at modules/gdscript/gdscript_analyzer.cpp:4843
#2  0x0000555558c6fb97 in GDScriptAnalyzer::reduce_call (this=0x7fffffffca30, 
    p_call=0x55557dddd570, p_is_await=false, p_is_root=true)
    at modules/gdscript/gdscript_analyzer.cpp:3095

Closes #77066.

[akien-mga]

Thanks!

[YuriSizov]

Cherry-picked for 4.0.4.