Local sva variables assignment is resulting in error.

[Humblefool14]

SBY 23:10:00 [ff_flat_basic] base: starting process "cd ff_flat_basic/src; yosys -ql ../model/design.log ../model/design.ys"
SBY 23:10:00 [ff_flat_cover] base: starting process "cd ff_flat_cover/src; yosys -ql ../model/design.log ../model/design.ys"
SBY 23:10:00 [ff_flat_basic] base: dv_lib_ff_flat_mem.sv:37: ERROR: Insufficient number of array indices for mem_nxt.
SBY 23:10:00 [ff_flat_cover] base: dv_lib_ff_flat_mem.sv:37: ERROR: Insufficient number of array indices for mem_nxt.

BITDATA and NUMADDR are arbitrary values.
reg [BITDATA-1:0] mem [0:NUMADDR-1];
reg [BITDATA-1:0] mem_nxt [0:NUMADDR-1];

always_comb begin
mem_nxt = mem;