Fix crash with malformed arguments (bug 6176).

sourcepawn/compiler/sc1.c

@@ -6652,6 +6652,10 @@ static void statement(int *lastindent,int allow_decl)
     }
 
     if (is_decl) {
+      if (!allow_decl) {
+        error(3);
+        return;
+      }
       lexpush();
       autozero = TRUE;
       lastst = tNEW;

sourcepawn/compiler/tests/fail-missing-arg-comma.sp

@@ -0,0 +1,4 @@
+stock void Function( float array1[ 3 ] float array2[ 3 ] )
+{
+
+}

sourcepawn/compiler/tests/fail-missing-arg-comma.txt

@@ -0,0 +1 @@
+(1) : error 001: expected token: ")", but found "-identifier-"