fix(compiler): Prevent panic when compiler is nil (#2942)

Resolves #2939

Author: andrewmbenton

internal/cmd/generate.go

@@ -348,7 +348,11 @@ func remoteGenerate(ctx context.Context, configPath string, conf *config.Config,
 func parse(ctx context.Context, name, dir string, sql config.SQL, combo config.CombinedSettings, parserOpts opts.Parser, stderr io.Writer) (*compiler.Result, bool) {
 	defer trace.StartRegion(ctx, "parse").End()
 	c, err := compiler.NewCompiler(sql, combo)
-	defer c.Close(ctx)
+	defer func() {
+		if c != nil {
+			c.Close(ctx)
+		}
+	}()
 	if err != nil {
 		fmt.Fprintf(stderr, "error creating compiler: %s\n", err)
 		return nil, true

internal/endtoend/testdata/bad_config/engine/query.sql

@@ -0,0 +1,2 @@
+-- name: Test :exec
+SELECT 1;

internal/endtoend/testdata/bad_config/engine/sqlc.yaml

@@ -0,0 +1,8 @@
+version: 2
+sql:
+- queries: query.sql
+  schema: query.sql
+  engine: "bad_engine"
+  gen:
+    go:
+      out: "db"

internal/endtoend/testdata/bad_config/engine/stderr.txt

@@ -0,0 +1 @@
+error creating compiler: unknown engine: bad_engine