VHDL - Index out range even If I made concurrent checking using when-else - logic

Question

I'm implementing a register file where I wanna read asynchronously and write on the rising edge.
I made concurrent checks on the addresses and the writing occurs inside a process.
However, it always cause me a fatal error and I don't know why!
Here's my code if anyone could help and tell me how can I read asynchronously and write on rising edge
Thank you!
library ieee;
use ieee.std_logic_1164.all;
use ieee.numeric_std.all;
entity RegFile is
port(
outData1 : out std_logic_vector(15 downto 0);
outData2 : out std_logic_vector(15 downto 0);
inData : in std_logic_vector(15 downto 0);
writeEn : in std_logic;
reg1Sel : in std_logic_vector(2 downto 0);
reg2Sel : in std_logic_vector(2 downto 0);
writeRegSel : in std_logic_vector(2 downto 0);
clk : in std_logic
);
end RegFile;
architecture Register_File of RegFile is
type registerFile is array(0 to 5) of std_logic_vector(15 downto 0);
signal registers : registerFile;
signal reg1Address,reg2Address : integer;
signal reg1FinalAddressing,reg2FinalAddressing : std_logic_vector(2 downto 0);
begin
--Conversion of logic vector to unsigned integer
reg1Address <= to_integer(unsigned(reg1Sel));
reg2Address <= to_integer(unsigned(reg2Sel));
reg1FinalAddressing <= reg1Sel when (reg1Address<6 ) else
(others => '0');
reg2FinalAddressing <= reg2Sel when (reg2Address<6 ) else
(others => '0');
outData1 <= registers(to_integer(unsigned(reg1FinalAddressing)));
outData2 <= registers(to_integer(unsigned(reg2FinalAddressing)));
process (clk) is
begin
-- Reading from Registers 1 and 2
if rising_edge(clk) then
-- Writing to Register file Case Enabled
if writeEn = '1' then
registers(to_integer(unsigned(writeRegSel))) <= inData;
-- Case a value being written to register file, it will be out simultaneously if
-- the register was already selected. (The updated values are being released instantly).
if reg1Sel = writeRegSel then
outData1 <= inData;
end if;
if reg2Sel = writeRegSel then
outData2 <= inData;
end if;
end if;
end if;
end process;
end Register_File;