add nil checking for thruster init functions

main.lua

@@ -241,11 +241,17 @@ function PropellerInit()
     local propellers = {}
 
     for _, v in ipairs(TransmissionTypes) do
-        table.insert(transmissions, peripheral.find(v))
+        local vlist = peripheral.find(v)
+        if vlist ~= nil and vlist[1] ~= nil then
+            table.insert(transmissions, vlist)
+        end
     end
 
     for _, v in ipairs(PropellerTypes) do
-        table.insert(propellers, peripheral.find(v))
+        local vlist = peripheral.find(v)
+        if vlist ~= nil and vlist[1] ~= nil then
+            table.insert(propellers, vlist)
+        end
     end
 
     for pi, pv in ipairs(propellers) do 
@@ -306,7 +312,10 @@ function ThrusterInit()
     local thrusters = {}
 
     for _, v in ipairs(ThrusterTypes) do
-        table.insert(thrusters, peripheral.find(v))
+        local vlist = peripheral.find(v)
+        if vlist ~= nil and vlist[1] ~= nil then
+            table.insert(thrusters, vlist)
+        end
     end
 
     for ti, tv in ipairs(thrusters) do