Remove incorrect assert.

If we run into the second preprocessor branch chain, the first branch
chain might have already set the maximum branch count on that level to
something > 0.

Fixes PR17645.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@193153 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/unittests/Format/FormatTest.cpp b/unittests/Format/FormatTest.cpp
index a7de81b..20132f9 100644
--- a/unittests/Format/FormatTest.cpp
+++ b/unittests/Format/FormatTest.cpp
@@ -2327,6 +2327,12 @@
                getLLVMStyleWithColumns(28));
   verifyFormat("#if 1\n"
                "int i;");
+  verifyFormat(
+      "#if 1\n"
+      "#endif\n"
+      "#if 1\n"
+      "#else\n"
+      "#endif\n");
 }
 
 TEST_F(FormatTest, FormatsJoinedLinesOnSubsequentRuns) {