Grammar police warning: The comma in “if it doesn’t crash, the bug is present” actually makes the intention more difficult to understand.
"if, it doesn't crash ..." nope
"if it, doesn't ..." nope
"if it doesn't, crash ... " nope
"if it doesn't crash, the " yep!
"if it doesn't crash the, bug ..." nope
"if it doesn't crash the bug, is ..." nope
"if it doesn't crash the bug is, present" nope.
When it is present, it does help to separate the if and then, particularly in the absence of the word "then".
Without the comma, the prefix "if it doesn't crash the bug" can be scanned as a viable clause, only to find that the suffix becomes a fragment.