Avoid a type mismatch that shows up in C++11.
Taken from <https://bugs.debian.org/853560>.

--- a/src/rtphint.cpp	2012-05-20 16:11:53.000000000 -0600
+++ b/src/rtphint.cpp	2017-05-16 10:25:26.930705191 -0600
@@ -339,7 +339,7 @@
                 pSlash = strchr(pSlash, '/');
                 if (pSlash != NULL) {
                     pSlash++;
-                    if (pSlash != '\0') {
+                    if (*pSlash != '\0') {
                         length = (uint32_t)strlen(pRtpMap) - (pSlash - pRtpMap);
                         *ppEncodingParams = (char *)MP4Calloc(length + 1);
                         strncpy(*ppEncodingParams, pSlash, length);
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<tr><td><span title='2021-12-13 17:48:25 +0100'>2021-12-13</span></td><td><a href='/guix/commit/gnu/packages/gkrellm.scm?id=8394619baceb118df92e355377fd543bb1aa501a'>gnu: Simplify package inputs.</a></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2020-03-07 01:41:23 +0100'>2020-03-07</span></td><td><a href='/guix/commit/gnu/packages/gkrellm.scm?id=64df1416c297af8ddff051bdbe3f2c001c5b8e1e'>gnu: gkrellm: Update to 2.3.11.</a></td><td>Tobias Geerinckx-Rice</td></tr>