Standard Error showing as 0

[Lindsey Buck]

Hi, I have posted my code below but I am wondering--is there a reason that for a couple of outcomes (college, i.e.) my standard errors are being reported as 0? I don't think this is correct...no stars showing up....thanks!

local i = 25
local j = `i' + 5
local k = 4
local d = 0.85
local distb1 "distp_cutoffb`k'"
capture erase table5.txt
use if agech >= `i' & agech <= `j' & inrange(`distb1',-`d',`d') using sample_data, clear
local controls_early2 "lincomeb02_1 lincomeb02_2 fsize02_1 fsize02_2 fsize_incomeb02 bweight_1 bweight_2"
local controlsc2 "lincomeb4_1 lincomeb4_2 fsize4_1 fsize4_2 fsize_incomeb4 father_figure4 male black dyear4_* dagech_4 dstate4_*"

foreach outcome in welfare unemployment foodstamps income posted employed financialstrain married_r economic_index college trade {
foreach race in all  { 
    foreach sample in male { 

    probit hstart eligb`k' `controlsc2' dstate`k'_* `controls_early2' if `outcome' != . & `race'_`sample' == 1, cluster(cluster`k')
    predict phat if e(sample)

    local condtb "if phat != . & `race'_`sample' == 1, cluster(cluster`k' idc) a(state`k')"

    reghdfe `outcome' eligb`k' distp_cutoffb4 distp_cutoffb4_2 `controlsc2' `controls_early2' `condtb' 
    su `outcome' if e(sample) & `distb1' > 0 & `distb1' <= 0.25
    scalar mean = r(mean)
    scalar stdv = r(sd)
    outreg2 using table5.xls, bra se excel  nocons ctitle("`outcome'-`race'_`sample'") addstat("control mean",mean,"sd",stdv) append
    
    drop phat
    
    }
}
}