Add NULL check to CallStack::toString

CallStack::toString() has a 0 default argument, which ends up getting
passed to strlen(), resulting in a crash.

Change-Id: If706aff8c400983670f49cdbb66e11191ac76e0e

parent 0e1e53e3

libs/utils/CallStack.cpp

+3 −1

Original line number	Diff line number	Diff line
		@@ -118,7 +118,9 @@ String8 CallStack::toString(const char* prefix) const {
		char line[MAX_BACKTRACE_LINE_LENGTH];
		format_backtrace_line(i, &mStack[i], &symbols[i],
		line, MAX_BACKTRACE_LINE_LENGTH);
		if (prefix) {
		str.append(prefix);
		}
		str.append(line);
		str.append("\n");
		}