Fix #12052: NewGRFs clearing industry cargo slots could fallback to default instead of empty.

Ensure the default label is cleared when NewGRF sets a produced/accepted cargo slot, so that default fallback isn't used.

src/newgrf.cpp

@@ -3790,6 +3790,7 @@ static ChangeInfoResult IndustriesChangeInfo(uint indid, int numinfo, int prop,
 					} else {
 						indsp->produced_cargo[i] = INVALID_CARGO;
 					}
+					indsp->produced_cargo_label[i] = CT_INVALID;
 				}
 				break;
 			}
@@ -3808,6 +3809,7 @@ static ChangeInfoResult IndustriesChangeInfo(uint indid, int numinfo, int prop,
 					} else {
 						indsp->accepts_cargo[i] = INVALID_CARGO;
 					}
+					indsp->accepts_cargo_label[i] = CT_INVALID;
 				}
 				break;
 			}