Fixes errors that I seem to have inadvertently introduced while preparing the final PR for 0673e3f :

    Fix wrong logic (current version sets the flag when an offset value is unequal zero)
    Check tool table offsets not the currently active tool offsets

Also

    Initialization for the flag in interp_setup

Author: Sigma1912

src/emc/rs274ngc/interp_convert.cc

@@ -6239,9 +6239,9 @@ int Interp::convert_tool_length_offset(int g_code,       //!< g_code being execu
     tool_offset.v = USER_TO_PROGRAM_LEN(settings->tool_table[idx].offset.v);
     tool_offset.w = USER_TO_PROGRAM_LEN(settings->tool_table[idx].offset.w);
     settings->g43_with_zero_offset =
-      (settings->tool_offset.tran.x || settings->tool_offset.tran.y || settings->tool_offset.tran.z ||
-       settings->tool_offset.a || settings->tool_offset.b || settings->tool_offset.c ||
-       settings->tool_offset.u || settings->tool_offset.v || settings->tool_offset.w);
+      !(tool_offset.tran.x || tool_offset.tran.y || tool_offset.tran.z ||
+        tool_offset.a || tool_offset.b || tool_offset.c ||
+        tool_offset.u || tool_offset.v || tool_offset.w);
   } else if (g_code == G_43_1) {
     tool_offset = settings->tool_offset;
     idx = -1;

src/emc/rs274ngc/interp_setup.cc

@@ -140,6 +140,7 @@ setup::setup() :
     tool_table{},
     traverse_rate (0.0),
     orient_offset (0.0),
+    g43_with_zero_offset(false),
 
     defining_sub(0),
     sub_name(NULL),