Restore ability to save any previously loaded specs before switching

Author: Wires77

src/Export/Main.lua

@@ -336,11 +336,13 @@ function main:LoadDatSource(value)
 	self.leagueLabel = nil
 	local reExportState = self.reExportGGPKData
 	self.reExportGGPKData = true
+	if self.datSource then
+		local out = io.open(self.datSource.spec..(self.datSource.spec:match("%.lua$") and "" or ".lua"), "w")
+		out:write('return ')
+		writeLuaTable(out, self.datSpecs, 1)
+		out:close()
+	end
 	self.datSource = value
-	local out = io.open(self.datSource.spec..(self.datSource.spec:match("%.lua$") and "" or ".lua"), "w")
-	out:write('return ')
-	writeLuaTable(out, self.datSpecs, 1)
-	out:close()
 	self.datSpecs = LoadModule(self.datSource.spec)
 	self:InitGGPK()
 	if USE_DAT64 then