Fix custom build export

(cherry picked from commit df1ebbb0aa7cd26c3753181761201afc0948deff)

platform/android/export/export.cpp

@@ -2155,6 +2155,8 @@ public:
 			if (!installed_android_build_template) {
 
 				err += TTR("Android build template not installed in the project. Install it from the Project menu.") + "\n";
+			} else {
+				r_missing_templates = false;
 			}
 
 			valid = installed_android_build_template && !r_missing_templates;