make sure state token values are fully initialized

cherry-picked from master
diff --git a/src/mesa/shader/arbprogparse.c b/src/mesa/shader/arbprogparse.c
index 38e174f..2fd356e 100644
--- a/src/mesa/shader/arbprogparse.c
+++ b/src/mesa/shader/arbprogparse.c
@@ -1767,7 +1767,7 @@
 {
    GLint idx;
    GLuint err = 0;
-   gl_state_index state_tokens[STATE_LENGTH];
+   gl_state_index state_tokens[STATE_LENGTH] = {0, 0, 0, 0, 0};
    GLfloat const_values[4];
 
    switch (*(*inst)++) {