fix(doc): check if modmt exists before trying to get module prop docs

nature/commands/doc.lua

@@ -58,6 +58,7 @@ commander.register('doc', function(args)
 			local propstr = ''
 			local modDesc = ''
 			local modmt = getmetatable(require(mod))
+			if modmt then
 				modDesc = modmt.__doc
 				if modmt.__docProp then
 					-- not all modules have docs for properties
@@ -70,6 +71,7 @@ commander.register('doc', function(args)
 				end
 				desc = string.format(modDocFormat, modDesc, propstr)
 			end
+		end
 		print(desc .. formattedFuncs)
 		f:close()