installer: fix how collection of in memory app configs is created (#74)

Was allocating non empty slice before, which followed by appends
would leave nil-s at the beginning of the slice.

Co-authored-by: Giorgi Lekveishvili <lekva@gl-mbp-m1-max.local>
diff --git a/core/installer/app.go b/core/installer/app.go
index 5791780..058c31b 100644
--- a/core/installer/app.go
+++ b/core/installer/app.go
@@ -349,7 +349,7 @@
 }
 
 func createApps(configs []string) []App {
-	ret := make([]App, len(configs))
+	ret := make([]App, 0)
 	for _, cfgFile := range configs {
 		cfg, err := readCueConfigFromFile(valuesTmpls, cfgFile)
 		if err != nil {