SilverSearcher: Fix crash in output parser

Neither parseFilePath nor parseText guarantee that index stays <
outputSize.

Change-Id: I087858cf6c1027fd04a7608c8ef10f4ce88348ef
Reviewed-by: Przemyslaw Gorszkowski <pgorszkowski@gmail.com>
Reviewed-by: Orgad Shaneh <orgads@gmail.com>

src/plugins/silversearcher/silversearcheroutputparser.cpp

@@ -46,7 +46,7 @@ QList<Utils::FileSearchResult> SilverSearcherOutputParser::parse()
             continue;
         }
         parseFilePath();
-        while (output[index] != '\n') {
+        while (index < outputSize && output[index] != '\n') {
             parseLineNumber();
             if (index >= outputSize - 1)
                 break;