Reset gamepad mapping before parsing

CONTRIBUTORS.md

@@ -274,6 +274,7 @@ video tutorials.
  - Elviss Strazdins
  - Paul Sultana
  - Nathan Sweet
+ - Ruben Sørensen
  - TTK-Bandit
  - Nuno Teixeira
  - Jared Tiala

README.md

@@ -120,7 +120,7 @@ information on what to include when reporting a bug.
 
 ## Changelog since 3.5
 
-None.
+ - Bugfix: Fixed stale gamepad mapping data when parsing mappings
 
 
 ## Contact

src/input.c

@@ -124,6 +124,8 @@ static _GLFWmapping* findValidMapping(const _GLFWjoystick* js)
 //
 static GLFWbool parseMapping(_GLFWmapping* mapping, const char* string)
 {
+    memset(mapping, 0, sizeof(*mapping));
+
     const char* c = string;
     size_t i, length;
     struct