run-tests: don't error when glob matched line ends with backslash

As part of writing another test, I triggered an array index error in
glob match processing code by having a (glob) line end in a single
backslash (which is the escape character).

Adding a simple bounds check prevents the error in run-tests.py.

tests/run-tests.py

@@ -1065,7 +1065,7 b' class TTest(Test):'
         while i < n:
             c = el[i]
             i += 1
-            if c == '\\' and el[i] in '*?\\/':
+            if c == '\\' and i < n and el[i] in '*?\\/':
                 res += el[i - 1:i + 1]
                 i += 1
             elif c == '*':

tests/test-run-tests.t

@@ -491,3 +491,17 b' test for --json'
   } (no-eol)
 
 #endif
+
+backslash on end of line with glob matching is handled properly
+
+  $ cat > test-glob-backslash.t << EOF
+  >   $ echo 'foo bar \\'
+  >   foo * \ (glob)
+  > EOF
+
+  $ $TESTDIR/run-tests.py --with-hg=`which hg` test-glob-backslash.t
+  .
+  # Ran 1 tests, 0 skipped, 0 warned, 0 failed.
+
+  $ rm -f test-glob-backslash.t
+